IC ( Inter-Integrated Circuit ; pronounced as “ eye-squared-see ” or “ eye-two-see ”), alternatively known as I2C or IIC , is a synchronous , multi-controller/multi-target (historically termed as multi-master/multi-slave ), single-ended , serial communication bus invented in 1982 by Philips Semiconductors . It is widely used for attaching lower-speed peripheral integrated circuits (ICs) to processors and microcontrollers in short-distance, intra-board communication.
101-982: Several competitors, such as Siemens , NEC , Texas Instruments , STMicroelectronics , Motorola , Nordic Semiconductor and Intersil , have introduced compatible IC products to the market since the mid-1990s. IC bus can be found in a wide range of electronics applications where simplicity and low manufacturing cost are more important than speed. PC components and systems which involve IC are serial presence detect (SPD) EEPROMs on dual in-line memory modules (DIMMs), Extended Display Identification Data (EDID) for monitors via VGA , DVI and HDMI connectors, accessing NVRAM chips, etc. Common I2C applications include reading hardware monitors, sensors, real-time clocks , controlling actuators, accessing low-speed DACs and ADCs , controlling simple LCD or OLED displays, changing computer display settings (e.g. backlight, contrast, hue, color balance) via Display Data Channel , and changing speaker volume. A particular strength of IC
202-433: A current source instead of a resistor to pull-up only SCL or both SCL and SDA, to accommodate higher bus capacitance and enable faster rise times. An important consequence of this is that multiple nodes may be driving the lines simultaneously. If any node is driving the line low, it will be low. Nodes that are trying to transmit a logical one (i.e. letting the line float high) can detect this and conclude that another node
303-406: A pull-up resistor is needed for each line. A logic "0" is output by pulling the line to ground, and a logic "1" is output by letting the line float (output high impedance ) so that the pull-up resistor pulls it high. A line is never actively driven high. This wiring allows multiple nodes to connect to the bus without short circuits from signal contention. High-speed systems (and some others) may use
404-409: A "two-wire interface" and not IC. To ensure a minimal bus throughput , SMBus places limits on how far clocks may be stretched. Hosts and targets adhering to those limits cannot block access to the bus for more than a short time, which is not a guarantee made by pure IC systems. Every controller monitors the bus for start and stop bits and does not start a message while another controller is keeping
505-458: A "void message" is usually harmless), so the next step is to pull SCL low. Except for the start and stop signals, the SDA line only changes while the clock is low; transmitting a data bit consists of pulsing the clock line high while holding the data line steady at the desired level. While SCL is low, the transmitter (initially the controller) sets SDA to the desired value and (after a small delay to let
606-561: A $ 100 million fund at the World Bank to support anti-corruption activities over 15 years, known as the "Siemens Integrity Initiative." Other substantial fines include a payment of ₦7 billion (US$ 46.57 million) to the Nigerian government in 2010, and a US$ 42.7 million penalty in Israel in 2014 to avoid charges of securities fraud. In 2006, Siemens purchased Bayer Diagnostics which was incorporated into
707-450: A 2 MHz clock but the processing throughput is similar to the 1 MHz 6800. The 8080 requires more clock cycles to execute a processor instruction. Due to their dynamic logic , the 6800 has a minimum clock rate of 100 kHz and the 8080 has a minimum clock rate of 500 kHz. Higher speed versions of both microprocessors were released by 1976. The 6501 requires an external 2-phase clock generator. The MOS Technology 6502 uses
808-551: A 7-bit address space , with a rarely used 10-bit extension. Common IC bus speeds are the 100 kbit/s standard mode and the 400 kbit/s fast mode . There is also a 10 kbit/s low-speed mode , but arbitrarily low clock frequencies are also allowed. Later revisions of IC can host more nodes and run at faster speeds (400 kbit/s fast mode , 1 Mbit/s fast mode plus , 3.4 Mbit/s high-speed mode , and 5 Mbit/s ultra-fast mode ). These speeds are more widely used on embedded systems than on PCs. Note that
909-495: A START and ends with a STOP: In a combined transaction, each read or write begins with a START and the target address. The START conditions after the first are also called repeated START bits. Repeated STARTs are not preceded by STOP conditions, which is how targets know that the next message is part of the same transaction. Any given target will only respond to certain messages, as specified in its product documentation. Pure IC systems support arbitrary message structures. SMBus
1010-533: A STOP is sent). There may be four potential modes of operation for a given bus device, although most devices only use a single role and its two modes: In addition to 0 and 1 data bits, the IC bus allows special START and STOP signals which act as message delimiters and are distinct from the data bits. (This is in contrast to the start bits and stop bits used in asynchronous serial communication , which are distinguished from data bits only by their timing.) The controller
1111-503: A US lawyer, as an independent director in charge of compliance and accepting oversight from Theo Waigel , a former German finance minister. Siemens implemented new anti-corruption policies, including a comprehensive anti-corruption handbook, online tools for due diligence and compliance, a confidential communications channel for employees, and a corporate disciplinary committee. This process involved hiring approximately 500 full-time compliance personnel worldwide. Siemens's bribery culture
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#17330851630061212-411: A clock from a crystal oscillator . The only exceptions are asynchronous circuits such as asynchronous CPUs . A clock signal might also be gated, that is, combined with a controlling signal that enables or disables the clock signal for a certain part of a circuit. This technique is often used to save power by effectively shutting down portions of a digital circuit when they are not in use, but comes at
1313-478: A combined message: first a write, then a read. The controller issues an ACK after each read byte except the last byte, and then issues a STOP. The EEPROM increments the address after each data byte transferred; multi-byte reads can retrieve the entire contents of the EEPROM using one combined message. At the physical layer , both SCL and SDA lines are an open-drain ( MOSFET ) or open-collector ( BJT ) bus design, thus
1414-569: A command which is issued by only one controller need not be idempotent, nor is it necessary for a specific command to be idempotent when some mutual exclusion mechanism ensures that only one controller can be caused to issue that command at any given time.) While IC only arbitrates between controllers, SMBus uses arbitration in three additional contexts, where multiple targets respond to the controller, and one gets its message through. Siemens Siemens AG ( German pronunciation: [ˈziːməns] or [-mɛns] )
1515-504: A common ground potential, which again restricts practical use to communication within the same PC board or small system of boards. The aforementioned reference design is a bus with a clock (SCL) and data (SDA) lines with 7-bit addressing. The bus has two roles for nodes, either controller (master) or target (slave): The bus is a multi-controller bus, which means that any number of controller nodes can be present. Additionally, controller and target roles may be changed between messages (after
1616-487: A company branch headed by another brother, Carl Heinrich von Siemens , opened in St Petersburg , Russia. In 1867, Siemens completed the monumental Indo-European telegraph line stretching over 11,000 km from London to Calcutta . In 1867, Werner von Siemens described a dynamo without permanent magnets. A similar system was also independently invented by Ányos Jedlik and Charles Wheatstone , but Siemens became
1717-411: A cost of increased complexity in timing analysis. Most modern synchronous circuits use only a "single phase clock" – in other words, all clock signals are (effectively) transmitted on 1 wire. In synchronous circuits , a "two-phase clock" refers to clock signals distributed on 2 wires, each with non-overlapping pulses. Traditionally one wire is called "phase 1" or "φ1" ( phi 1), the other wire carries
1818-458: A design with a smaller overall gate count but usually at some penalty in design difficulty and performance. Metal oxide semiconductor (MOS) ICs typically used dual clock signals (a two-phase clock) in the 1970s. These were generated externally for both the Motorola 6800 and Intel 8080 microprocessors. The next generation of microprocessors incorporated the clock generation on chip. The 8080 uses
1919-466: A fine as high as $ 5 billion, the final amount was significantly less, in part due to Siemens's cooperation with the investigators, the upcoming change in the US administration, and Siemens's role as a US military contractor . The payments included $ 450 million in fines and penalties and a forfeiture of $ 350 million in profits in the US. Siemens also revamped its compliance systems, appointing Peter Y. Solmssen ,
2020-667: A global revenue of around €78 billion in 2023. The company is a component of the DAX and Euro Stoxx 50 stock market indices. As of December 2023, Siemens is the second largest German company by market capitalization . As of 2023, the principal divisions of Siemens are Digital Industries, Smart Infrastructure, Mobility , and Financial Services , with Siemens Mobility operating as an independent entity. Major business divisions that were once part of Siemens before being spun off include semiconductor manufacturer Infineon Technologies (1999), Siemens Mobile (2005), Gigaset Communications (2008),
2121-401: A legally independent company: Siemens Electromechanical Components GmbH & Co. KG, (which, later that year, was sold to Tyco International Ltd for approximately $ 1.1 billion. In the same year, Siemens Nixdorf Informationssysteme AG became part of Fujitsu Siemens Computers , with its retail banking technology group becoming Wincor Nixdorf . In 2000, Shared Medical Systems Corporation
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#17330851630062222-567: A multi-national bribery scandal. Among the various incidents was the Siemens Greek bribery scandal , where the company was accused of deals with Greek government officials during the 2004 Summer Olympics . This case, along with others, triggered legal investigations in Germany, initiated by prosecutors in Italy, Liechtenstein, and Switzerland, and later followed by an American investigation in 2006 due to
2323-413: A particular address in the EEPROM, a combined message is used. After a START, the controller first writes that chip's bus address with the direction bit clear ( write ) and then the two bytes of EEPROM data address. It then sends a (repeated) START and the EEPROM's bus address with the direction bit set ( read ). The EEPROM will then respond with the data bytes beginning at the specified EEPROM data address —
2424-417: A rate slower than the worst-case internal propagation delays . In some cases, more than one clock cycle is required to perform a predictable action. As ICs become more complex, the problem of supplying accurate and synchronized clocks to all the circuits becomes increasingly difficult. The preeminent example of such complex chips is the microprocessor , the central component of modern computers, which relies on
2525-688: A stricter usage. One purpose of SMBus is to promote robustness and interoperability. Accordingly, modern IC systems incorporate some policies and rules from SMBus, sometimes supporting both IC and SMBus, requiring only minimal reconfiguration either by commanding or output pin use. System management for PC systems uses SMBus whose pins are allocated in both conventional PCI and PCI Express connectors. IC uses only two signals : serial data line (SDA) and serial clock line (SCL). Both are bidirectional and pulled up with resistors . Typical voltages used are +5 V or +3.3 V, although systems with other voltages are permitted. The IC reference design has
2626-404: A target inefficiently allows only 1 byte of data to be transferred, the data rate will be less than half the peak bit rate. The number of nodes which can exist on a given IC bus is limited by the address space and also by the total bus capacitance of 400 pF , which restricts practical communication distances to a few meters. The relatively high impedance and low noise immunity requires
2727-498: A tree such as an H-tree ) distributes the clock signal(s) from a common point to all the elements that need it. Since this function is vital to the operation of a synchronous system, much attention has been given to the characteristics of these clock signals and the electrical networks used in their distribution. Clock signals are often regarded as simple control signals; however, these signals have some very special characteristics and attributes. Clock signals are typically loaded with
2828-509: A write command are treated as a command or address. Those bytes determine how subsequent written bytes are treated or how the target responds on subsequent reads. Most SMBus operations involve single-byte commands. One specific example is the 24C32 type EEPROM , which uses two request bytes that are called Address High and Address Low. (Accordingly, these EEPROMs are not usable by pure SMBus hosts, which support only single-byte commands or addresses.) These bytes are used for addressing bytes within
2929-452: Is a German multinational technology conglomerate . It is focused on industrial automation , distributed energy resources , rail transport and health technology . Siemens is the largest industrial manufacturing company in Europe, and holds the position of global market leader in industrial automation and industrial software . The origins of the conglomerate can be traced back to 1847 to
3030-423: Is active at the same time. When used on SCL, this is called clock stretching and is a flow-control mechanism for targets. When used on SDA, this is called arbitration and ensures that there is only one transmitter at a time. When idle, both lines are high. To start a transaction, SDA is pulled low while SCL remains high. It is illegal to transmit a stop marker by releasing SDA to float high again (although such
3131-480: Is communicating with the target may not finish the transmission of the current bit, but must wait until the clock line actually goes high. If the target is clock-stretching, the clock line will still be low (because the connections are open-drain ). The same is true if a second, slower, controller tries to drive the clock at the same time. (If there is more than one controller, all but one of them will normally lose arbitration.) The controller must wait until it observes
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3232-420: Is in the form of a square wave with a 50% duty cycle . Circuits using the clock signal for synchronization may become active at either the rising edge, falling edge, or, in the case of double data rate , both in the rising and in the falling edges of the clock cycle. Most integrated circuits (ICs) of sufficient complexity use a clock signal in order to synchronize different parts of the circuit, cycling at
3333-452: Is initially in controller transmit mode by sending a START followed by the 7-bit address of the target it wishes to communicate with, which is finally followed by a single bit representing whether it wishes to write (0) to or read (1) from the target. If the target exists on the bus then it will respond with an ACK bit (active low for acknowledged) for that address. The controller then continues in either transmit or receive mode (according to
3434-560: Is one of the primary reasons for the increasing significance of clock distribution on synchronous performance. Finally, the control of any differences and uncertainty in the arrival times of the clock signals can severely limit the maximum performance of the entire system and create catastrophic race conditions in which an incorrect data signal may latch within a register. Most synchronous digital systems consist of cascaded banks of sequential registers with combinational logic between each set of registers. The functional requirements of
3535-481: Is restricted to nine of those structures, such as read word N and write word N , involving a single target. PMBus extends SMBus with a Group protocol, allowing multiple such SMBus transactions to be sent in one combined message. The terminating STOP indicates when those grouped actions should take effect. For example, one PMBus operation might reconfigure three power supplies (using three different IC target addresses), and their new configurations would take effect at
3636-400: Is the capability of a microcontroller to control a network of device chips with just two general-purpose I/O pins and software. Many other bus technologies used in similar applications, such as Serial Peripheral Interface Bus (SPI), require more pins and signals to connect multiple devices. System Management Bus (SMBus), defined by Intel and Duracell in 1994, is a subset of IC, defining
3737-577: Is the intervals before or after the acknowledgment bit which are used. For example, if the target is a microcontroller , its IC interface could stretch the clock after each byte, until the software decides whether to send a positive acknowledgment or a NACK. Clock stretching is the only time in IC where the target drives SCL. Many targets do not need to clock stretch and thus treat SCL as strictly an input with no circuitry to drive it. Some controllers, such as those found inside custom ASICs may not support clock stretching; often these devices will be labeled as
3838-426: Is transmitting. The first node to notice such a difference is the one that loses arbitration: it stops driving SDA. If it is a controller, it also stops driving SCL and waits for a STOP; then it may try to reissue its entire message. In the meantime, the other node has not noticed any difference between the expected and actual levels on SDA and therefore continues transmission. It can do so without problems because so far
3939-429: Is used like a metronome to synchronize actions of digital circuits . In a synchronous logic circuit, the most common type of digital circuit, the clock signal is applied to all storage devices, flip-flops and latches, and causes them all to change state simultaneously, preventing race conditions . A clock signal is produced by an electronic oscillator called a clock generator . The most common clock signal
4040-399: Is wasted in the driving transistors. In reversible computing , inductors can be used to store this energy and reduce the energy loss, but they tend to be quite large. Alternatively, using a sine wave clock, CMOS transmission gates and energy-saving techniques, the power requirements can be reduced. The most effective way to get the clock signal to every part of a chip that needs it, with
4141-818: The BenQ-Siemens division. Also in 2005 Siemens acquired Flender Holding GmbH ( Bocholt , Germany, gears/industrial drives), Bewator AB (building security systems), Wheelabrator Air Pollution Control, Inc. (Industrial and power station dust control systems), AN Windenergie GmbH. (Wind energy), Power Technologies Inc. ( Schenectady , USA, energy industry software and training), CTI Molecular Imaging ( Positron emission tomography and molecular imaging systems), Myrio ( IPTV systems), Shaw Power Technologies International Ltd (UK/USA, electrical engineering consulting, acquired from Shaw Group ), and Transmitton ( Ashby de la Zouch UK, rail and other industry control and asset management). Beginning in 2005, Siemens became embroiled in
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4242-754: The Cumann na nGaedheal government. Siemens (at the time: Siemens-Schuckert ) exploited the forced labour of deported people in extermination camps . The company owned a plant in Auschwitz concentration camp . Siemens exploited the forced labour of women deported to the Ravensbrück concentration camp ; a Siemens factory was located in front of the camp. During the final years of World War II , numerous plants and factories in Berlin and other major cities were destroyed by Allied air raids. To prevent further losses, manufacturing
4343-620: The European Commission for price fixing in EU electricity markets through a cartel involving 11 companies, including ABB , Alstom , Fuji Electric , Hitachi Japan , AE Power Systems, Mitsubishi Electric Corp , Schneider , Areva , Toshiba and VA Tech . According to the commission, "between 1988 and 2004, the companies rigged bids for procurement contracts, fixed prices, allocated projects to each other, shared markets and exchanged commercially important and confidential information." Siemens
4444-606: The Siemens-Reiniger-Werke AG (SRW), the third of the so-called parent companies that merged in 1966 to form the present-day Siemens AG. In the 1920s, Siemens constructed the Ardnacrusha Hydro Power station on the River Shannon in the then Irish Free State , and it was a world first for its design. The company is remembered for its desire to raise the wages of its underpaid workers, only to be overruled by
4545-578: The Telegraphen Bau-Anstalt von Siemens & Halske established in Berlin by Werner von Siemens and Johann Georg Halske . In 1966, the present-day corporation emerged from the merger of three companies: Siemens & Halske , Siemens-Schuckert , and Siemens-Reiniger-Werke . Today headquartered in Munich and Berlin, Siemens and its subsidiaries employ approximately 320,000 people worldwide and reported
4646-648: The Western Digital MCP-1600 chipset used in the DEC LSI-11 . Four phase clocks have only rarely been used in newer CMOS processors such as the DEC WRL MultiTitan microprocessor. and in Intrinsity 's Fast14 technology. Most modern microprocessors and microcontrollers use a single-phase clock. Many modern microcomputers use a " clock multiplier " which multiplies a lower frequency external clock to
4747-410: The "phase 2" or "φ2" signal. Because the two phases are guaranteed non-overlapping, gated latches rather than edge-triggered flip-flops can be used to store state information so long as the inputs to latches on one phase only depend on outputs from latches on the other phase. Since a gated latch uses only four gates versus six gates for an edge-triggered flip-flop, a two phase clock can lead to
4848-537: The 1950s, and from their new base in Bavaria , S&H started to manufacture computers , semiconductor devices , washing machines , and pacemakers . In 1966, Siemens & Halske (S&H, founded in 1847), Siemens-Schuckertwerke (SSW, founded in 1903) and Siemens-Reiniger-Werke (SRW, founded in 1932) merged to form Siemens AG. In 1969, Siemens formed Kraftwerk Union with AEG by pooling their nuclear power businesses. The company's first digital telephone exchange
4949-534: The 1990s. In 1993–1994, Siemens C651 electric trains for Singapore's Mass Rapid Transit (MRT) system were built in Austria. In 1997, Siemens agreed to sell the defence arm of Siemens Plessey to British Aerospace (BAe) and a German aerospace company, DaimlerChrysler Aerospace . BAe and DASA acquired the British and German divisions of the operation respectively. In October 1997, Siemens Financial Services (SFS)
5050-458: The 32 kbit (or 4 kB ) EEPROM address space. The same two-byte addressing is also used by larger EEPROMs, like the 24C512 which stores 512 kbits (or 64 kB). Writing data to and reading from these EEPROMs uses a simple protocol: the address is written, and then data is transferred until the end of the message. The data transfer part of the protocol can cause trouble on the SMBus, since
5151-487: The American division in 1979. AMD closed Advanced Micro Computers in late 1981 after switching focus to manufacturing second-source Intel x86 microprocessors. In 1985, Siemens bought Allis-Chalmers ' interest in the partnership company Siemens-Allis (formed 1978) which supplied electrical control equipment. It was incorporated into Siemens's Energy and Automation division. In 1987, Siemens reintegrated Kraftwerk Union,
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#17330851630065252-534: The Industrial Systems Division of Texas Instruments , based in Johnson City, Tennessee . This division was organized as Siemens Industrial Automation, and was later absorbed by Siemens Energy and Automation, Inc. In 1992, Siemens bought out IBM 's half of ROLM (Siemens had bought into ROLM five years earlier), thus creating SiemensROLM Communications; eventually dropping ROLM from the name later in
5353-477: The Medical Solutions Diagnostics division on 1 January 2007, also in 2006 Siemens acquired Controlotron (New York) (ultrasonic flow meters), and also in 2006 Siemens acquired Diagnostic Products Corp., Kadon Electro Mechanical Services Ltd. (now TurboCare Canada Ltd.), Kühnle, Kopp, & Kausch AG, Opto Control, and VistaScape Security Systems. In January 2007, Siemens was fined €396 million by
5454-617: The Power Generation division of Siemens AG. Other parts of the company were acquired by Robert Bosch GmbH at the same time. Also, Moore Products Co. of Spring House, PA USA was acquired by Siemens Energy & Automation, Inc. In 2001, Chemtech Group of Brazil was incorporated into the Siemens Group; it provides industrial process optimisation, consultancy and other engineering services. Also in 2001, Siemens formed joint venture Framatome with Areva SA of France by merging much of
5555-446: The SCL is always controlled by the controller. After the acknowledge bit, the clock line is low and the controller may do one of three things: One of the more significant features of the IC protocol is clock stretching. An addressed target device may hold the clock line (SCL) low after receiving (or sending) a byte, indicating that it is not yet ready to process more data. The controller that
5656-490: The US and Germany in what was, at the time, the largest bribery fine in history. In addition, the company was required to invest $ 1 billion in developing and maintaining new internal compliance procedures. Siemens admitted to violating the accounting provisions of the Foreign Corrupt Practices Act , while its Bangladesh and Venezuela subsidiaries pleaded guilty to paying bribes. Despite initial expectations of
5757-517: The analog circuitry and cause noise . Such sine wave clocks are often differential signals , because this type of signal has twice the slew rate , and therefore half the timing uncertainty, of a single-ended signal with the same voltage range. Differential signals radiate less strongly than a single line. Alternatively, a single line shielded by power and ground lines can be used. In CMOS circuits, gate capacitances are charged and discharged continually. A capacitor does not dissipate energy, but energy
5858-481: The appropriate clock rate of the microprocessor. This allows the CPU to operate at a much higher frequency than the rest of the computer, which affords performance gains in situations where the CPU does not need to wait on an external factor (like memory or input/output ). The vast majority of digital devices do not require a clock at a fixed, constant frequency. As long as the minimum and maximum clock periods are respected,
5959-413: The bit rates are quoted for the transfers between controller (master) and target (slave) without clock stretching or other hardware overhead. Protocol overheads include a target address and perhaps a register address within the target device, as well as per-byte ACK/NACK bits. Thus the actual transfer rate of user data is lower than those peak bit rates alone would imply. For example, if each interaction with
6060-404: The bus busy. However, two controllers may start transmission at about the same time; in this case, arbitration occurs. Target transmit mode can also be arbitrated, when a controller addresses multiple targets, but this is less common. In contrast to protocols (such as Ethernet ) that use random back-off delays before issuing a retry, IC has a deterministic arbitration policy. Each transmitter checks
6161-429: The careful insertion of pipeline registers into equally spaced time windows to satisfy critical worst-case timing constraints . The proper design of the clock distribution network helps ensure that critical timing requirements are satisfied and that no race conditions exist (see also clock skew ). The delay components that make up a general synchronous system are composed of the following three individual subsystems:
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#17330851630066262-432: The clock line going high, and an additional minimal time (4 μs for standard 100 kbit/s IC) before pulling the clock low again. Although the controller may also hold the SCL line low for as long as it desires (this is not allowed since Rev. 6 of the protocol – subsection 3.1.1), the term "clock stretching" is normally used only when targets do it. Although in theory any clock pulse may be stretched, generally it
6363-402: The companies' nuclear businesses. In 2002, Siemens sold some of its business activities to Kohlberg Kravis Roberts & Co. L.P. (KKR), with its metering business included in the sale package. In 2002, Siemens abandoned the solar photovoltaic industry by selling its participation in a joint-venture company, established in 2001 with Shell and E.ON , to Shell. In 2003, Siemens acquired
6464-506: The company an infusion of cash to increase its product lines. The two companies also jointly established Advanced Micro Computers (AMC), located in Silicon Valley and in Germany, allowing AMD to enter the microcomputer development and manufacturing field, in particular based on AMD's second-source Zilog Z8000 microprocessors. When the two companies' vision for Advanced Micro Computers diverged, AMD bought out Siemens's stake in
6565-553: The company built the first long-distance telegraph line in Europe: 500 km from Berlin to Frankfurt am Main . In 1850, the founder's younger brother, Carl Wilhelm Siemens, later Sir William Siemens , started to represent the company in London. The London agency became a branch office in 1858. In the 1850s, the company was involved in building long-distance telegraph networks in Russia. In 1855,
6666-645: The company opened an office in San Jose. On 7 March 2003, the company announced that it planned to gain 10 per cent of the mainland China market for handsets. On 18 March 2003, the company unveiled the latest in its series of Xelibri fashion phones. In 2004, the wind energy company Bonus Energy in Brande , Denmark was acquired, forming Siemens Wind Power division. Also in 2004, Siemens invested in Dasan Networks (South Korea, broadband network equipment) acquiring ~40% of
6767-475: The company's activities while listed on US stock exchanges. Investigations found that Siemens had a pattern of bribing officials to secure contracts, with the company spending approximately $ 1.3 billion on bribes across several countries, and maintaining separate accounting records to conceal this. Following the investigations, Siemens settled in December 2008, paying a combined total of approximately $ 1.6 billion to
6868-430: The controller is in controller receive mode, and the target is in target transmit mode.) An IC transaction may consist of multiple messages. The controller terminates a message with a STOP condition if this is the end of the transaction or it may send another START condition to retain control of the bus for another message (a "combined format" transaction). IC defines basic types of transactions, each of which begins with
6969-419: The controller wishes to write to the target, then it repeatedly sends a byte with the target sending an ACK bit. (In this situation, the controller is in controller transmit mode, and the target is in target receive mode.) If the controller wishes to read from the target, then it repeatedly receives a byte from the target, the controller sending an ACK bit after every byte except the last one. (In this situation,
7070-641: The conviction of two former executives in 2007 for bribing Italian energy company Enel , a settlement with the Greek government in 2012 for 330 million euros over the Greek bribery scandal, and a guilty plea in 2014 from former Siemens executive Andres Truppel for channeling nearly $ 100 million in bribes to Argentine government officials. Siemens also faced repercussions from the World Bank due to fraudulent practices by its Russian affiliate. In 2009, Siemens agreed not to bid on World Bank projects for two years and to establish
7171-459: The data bytes are not preceded by a count, and more than 32 bytes can be transferred at once. IC EEPROMs smaller than 32 kbit, like the 2 kbit 24C02, are often used on the SMBus with inefficient single-byte data transfers to overcome this problem. A single message writes to the EEPROM. After the START, the controller sends the chip's bus address with the direction bit clear ( write ), then sends
7272-545: The data stages. Arbitration occurs very rarely, but is necessary for proper multi-controller support. As with clock stretching, not all devices support arbitration. Those that do, generally label themselves as supporting "multi-controller" communication. One case which must be handled carefully in multi-controller IC implementations is that of the controllers talking to each other. One controller may lose arbitration to an incoming message, and must change its role from controller to target in time to acknowledge its own address. In
7373-405: The digital system are satisfied by the logic stages. Each logic stage introduces delay that affects timing performance, and the timing performance of the digital design can be evaluated relative to the timing requirements by a timing analysis. Often special consideration must be made to meet the timing requirements. For example, the global performance and local timing requirements may be satisfied by
7474-407: The extremely rare case that two controllers simultaneously send identical messages, both will regard the communication as successful, but the target will only see one message. For this reason, when a target can be accessed by multiple controllers, every command recognized by the target either must be idempotent or must be guaranteed never to be issued by two controllers at the same time. (For example,
7575-627: The first company to build such devices. In 1881, a Siemens AC Alternator driven by a watermill was used to power the world's first electric street lighting in the town of Godalming , United Kingdom. The company continued to grow and diversified into electric trains and light bulbs . In 1885, Siemens sold one of its generators to George Westinghouse , thereby enabling Westinghouse to begin experimenting with AC networks in Pittsburgh, Pennsylvania. In 1887, Siemens opened its first office in Japan. In 1890,
7676-701: The flow division of Danfoss and incorporated it into the Automation and Drives division. Also in 2003 Siemens acquired IndX software (realtime data organisation and presentation). The same year in an unrelated development Siemens reopened its office in Kabul . Also in 2003 agreed to buy Alstom Industrial Turbines; a manufacturer of small, medium and industrial gas turbines for €1.1 billion. On 11 February 2003, Siemens planned to shorten phones' shelf life by bringing out annual Xelibri lines, with new devices launched as spring -summer and autumn-winter collections. On 6 March 2003,
7777-773: The founder retired and left the running of the company to his brother Carl and sons Arnold and Wilhelm. In 1892, Siemens was contracted to construct the Hobart electric tramway in Tasmania , Australia , as it increased its markets. The system opened in 1893 and became the first complete electric tram network in the Southern Hemisphere. Siemens & Halske (S & H) was incorporated in 1897 and then merged parts of its activities with Schuckert & Co., Nuremberg, in 1903 to become Siemens-Schuckert . In 1907, Siemens ( Siemens & Halske and Siemens-Schuckert ) had 34,324 employees and
7878-488: The greatest fanout and operate at the highest speeds of any signal within the synchronous system. Since the data signals are provided with a temporal reference by the clock signals, the clock waveforms must be particularly clean and sharp. Furthermore, these clock signals are particularly affected by technology scaling (see Moore's law ), in that long global interconnect lines become significantly more resistive as line dimensions are decreased. This increased line resistance
7979-893: The implementation of the 1999 OECD Anti-Bribery Convention , Siemens started using off-shore accounts to hide its bribery. During the investigation, key player Reinhard Siekaczek, a mid-level executive in the telecommunications unit, provided critical evidence. He disclosed that he had managed an annual global bribery budget of $ 40 to $ 50 million and provided information about the company's 2,700 worldwide contractors, who were typically used to channel money to government officials. Notable instances of bribery included substantial payments in Argentina, Israel, Venezuela, China, Nigeria, and Russia to secure large contracts. The investigation resulted in multiple prosecutions and settlements with various governments, as well as legal action against Siemens employees and those who received bribes. Noteworthy cases include
8080-457: The level of the data line (SDA) and compares it with the levels it expects; if they do not match, that transmitter has lost arbitration and drops out of this protocol interaction. If one transmitter sets SDA to 1 (not driving a signal) and a second transmitter sets it to 0 (pull to ground), the result is that the line is low. The first transmitter then observes that the level of the line is different from that expected and concludes that another node
8181-434: The lowest skew , is a metal grid. In a large microprocessor, the power used to drive the clock signal can be over 30% of the total power used by the entire chip. The whole structure with the gates at the ends and all amplifiers in between have to be loaded and unloaded every cycle. To save energy, clock gating temporarily shuts off part of the tree. The clock distribution network (or clock tree , when this network forms
8282-435: The memory storage elements, the logic elements, and the clocking circuitry and distribution network. Novel structures are currently under development to ameliorate these issues and provide effective solutions. Important areas of research include resonant clocking techniques ("resonant clock mesh"), on-chip optical interconnect, and local synchronization methodologies. Adapted from Eby Friedman Archived 2014-08-12 at
8383-457: The photonics business Osram (2013), Siemens Healthineers (2017), and Siemens Energy (2020). Siemens & Halske was founded by Werner von Siemens and Johann Georg Halske on 1 October 1847. Based on the telegraph , their invention used a needle to point to the sequence of letters, instead of using Morse code . The company, then called Telegraphen-Bauanstalt von Siemens & Halske , opened its first workshop on 12 October. In 1848,
8484-412: The read/write bit it sent), and the target continues in the complementary mode (receive or transmit, respectively). The address and the data bytes are sent most significant bit first. The start condition is indicated by a high-to-low transition of SDA with SCL high; the stop condition is indicated by a low-to-high transition of SDA with SCL high. All other transitions of SDA take place with SCL low. If
8585-448: The receiver has seen the bit, then pulls it low again. This completes transmission of one bit. After every 8 data bits in one direction, an "acknowledge" bit is transmitted in the other direction. The transmitter and receiver switch roles for one bit, and the original receiver transmits a single "0" bit (ACK) back. If the transmitter sees a "1" bit (NACK) instead, it learns that: Only the SDA line changes direction during acknowledge bits;
8686-522: The same 2-phase logic internally, but also includes a two-phase clock generator on-chip, so it only needs a single phase clock input, simplifying system design. Some early integrated circuits use four-phase logic , requiring a four phase clock input consisting of four separate, non-overlapping clock signals. This was particularly common among early microprocessors such as the National Semiconductor IMP-16 , Texas Instruments TMS9900 , and
8787-709: The same time: when they receive that STOP. With only a few exceptions, neither IC nor SMBus define message semantics, such as the meaning of data bytes in messages. Message semantics are otherwise product-specific. Those exceptions include messages addressed to the IC general call address (0x00) or to the SMBus Alert Response Address ; and messages involved in the SMBus Address Resolution Protocol (ARP) for dynamic address allocation and management. In practice, most targets adopt request-response control models, where one or more bytes following
8888-508: The shares, Nokia Siemens disinvested itself of the shares in 2008. The same year Siemens acquired Photo-Scan (UK, CCTV systems), US Filter Corporation (water and Waste Water Treatment Technologies/ Solutions, acquired from Veolia ), Huntsville Electronics Corporation (automobile electronics, acquired from Chrysler ), and Chantry Networks ( WLAN equipment). In 2005, Siemens sold the Siemens mobile manufacturing business to BenQ , forming
8989-417: The signal has been exactly as it expected; no other transmitter has disturbed its message. If the two controllers are sending a message to two different targets, the one sending the lower target address always "wins" arbitration in the address stage. Since the two controllers may send messages to the same target address, and addresses sometimes refer to multiple targets, arbitration must sometimes continue into
9090-726: The time between clock edges can vary widely from one edge to the next and back again. Such digital devices work just as well with a clock generator that dynamically changes its frequency, such as spread-spectrum clock generation , dynamic frequency scaling , etc. Devices that use static logic do not even have a maximum clock period (or in other words, minimum clock frequency); such devices can be slowed and paused indefinitely, then resumed at full clock speed at any later time. Some sensitive mixed-signal circuits , such as precision analog-to-digital converters , use sine waves rather than square waves as their clock signals, because square waves contain high-frequency harmonics that can interfere with
9191-434: The two-byte address of data within the EEPROM and then sends data bytes to be written starting at that address, followed by a STOP. When writing multiple bytes, all the bytes must be in the same 32-byte page. While it is busy saving those bytes to memory, the EEPROM will not respond to further IC requests. (That is another incompatibility with SMBus: SMBus devices must always respond to their bus addresses.) To read starting at
9292-578: The unit overseeing nuclear power business. In 1987, Siemens acquired Kongsberg Offshore from the Norwegian Government, selling it on to FMC Technologies in 1993 In 1989, Siemens bought the solar photovoltaic business, including 3 solar module manufacturing plants, from industry pioneer ARCO Solar, owned by oil firm ARCO . In 1991, Siemens acquired Nixdorf Computer and renamed it Siemens Nixdorf Informationssysteme , in order to produce personal computers . In October 1991, Siemens acquired
9393-466: The value propagate) lets SCL float high. The controller then waits for SCL to actually go high; this will be delayed by the finite rise time of the SCL signal (the RC time constant of the pull-up resistor and the parasitic capacitance of the bus) and may be additionally delayed by a target's clock stretching. Once SCL is high, the controller waits a minimum time (4 μs for standard-speed IC) to ensure that
9494-586: Was acquired by the Siemens's Medical Engineering Group, eventually becoming part of Siemens Medical Solutions . Also in 2000, Atecs-Mannesman was acquired by Siemens, The sale was finalised in April 2001 with 50% of the shares acquired, acquisition, Mannesmann VDO AG merged into Siemens Automotive forming Siemens VDO Automotive AG, Atecs Mannesmann Dematic Systems merged into Siemens Production and Logistics forming Siemens Dematic AG, Mannesmann Demag Delaval merged into
9595-579: Was determined much of the book contained false claims although the trial itself publicized Siemens's history in Nazi Germany. The company supplied electrical parts to Nazi concentration camps and death camps . The factories had poor working conditions, where malnutrition and death were common. Also, the scholarship has shown that the camp factories were created, run, and supplied by the SS , in conjunction with company officials, sometimes high-level officials. In
9696-539: Was founded to act as a competence center for financing issues and as a manager of financial risks within Siemens. In 1998, Siemens acquired Westinghouse Power Generation for more than $ 1.5 billion from the CBS Corporation and moving Siemens from third to second in the world power generation market. In 1999, Siemens's semiconductor operations were spun off into a new company called Infineon Technologies . Its Electromechanical Components operations were converted into
9797-404: Was given the highest fine of €396 million, more than half of the total, for its alleged leadership role in the activity. Clock signal In electronics and especially synchronous digital circuits , a clock signal (historically also known as logic beat ) is an electronic logic signal ( voltage or current ) which oscillates between a high and a low state at a constant frequency and
9898-409: Was not new; it was highlighted as far back as 1914 when both Siemens and Vickers were involved in a scandal over bribes paid to Japanese naval authorities . The company resorted to bribery as it sought to expand its business in the developing world after World War II. Up until 1999, bribes were a tax-deductible business expense in Germany, with no penalties for bribing foreign officials. However, with
9999-497: Was produced in 1980, and in 1988, Siemens and GEC acquired the UK defence and technology company Plessey . Plessey's holdings were split, and Siemens took over the avionics , radar and traffic control businesses—as Siemens Plessey . In 1977, Advanced Micro Devices (AMD) entered into a joint venture with Siemens, which wanted to enhance its technology expertise and enter the American market. Siemens purchased 20% of AMD's stock, giving
10100-576: Was the seventh-largest company in the German empire by number of employees. (see List of German companies by employees in 1907 ) In 1919, S & H and two other companies jointly formed the Osram lightbulb company. During the 1920s and 1930s, S & H started to manufacture radios , television sets , and electron microscopes . In 1932, Reiniger, Gebbert & Schall (Erlangen), Phönix AG (Rudolstadt) and Siemens-Reiniger-Veifa mbH (Berlin) merged to form
10201-434: Was therefore moved to alternative places and regions not affected by the air war. The goal was to secure continued production of important war-related and everyday goods. According to records, Siemens was operating almost 400 alternative or relocated manufacturing plants at the end of 1944 and in early 1945. In 1972, Siemens sued German satirist F.C. Delius for his satirical history of the company, Unsere Siemens-Welt , and it
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