IEEE 488
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| Female IEEE 488 connector | |||
| Pin 1 | DIO1 | Data input/output bit. | |
|---|---|---|---|
| Pin 2 | DIO2 | Data input/output bit. | |
| Pin 3 | DIO3 | Data input/output bit. | |
| Pin 4 | DIO4 | Data input/output bit. | |
| Pin 5 | EOI | End-or-identify. | |
| Pin 6 | DAV | Data valid. | |
| Pin 7 | NRFD | Not ready for data. | |
| Pin 8 | NDAC | Not data accepted. | |
| Pin 9 | IFC | Interface clear. | |
| Pin 10 | SRQ | Service request. | |
| Pin 11 | ATN | Attention. | |
| Pin 12 | SHIELD | ||
| Pin 13 | DIO5 | Data input/output bit. | |
| Pin 14 | DIO6 | Data input/output bit. | |
| Pin 15 | DIO7 | Data input/output bit. | |
| Pin 16 | DIO8 | Data input/output bit. | |
| Pin 17 | REN | Remote enable. | |
| Pin 18 | GND | (wire twisted with DAV) | |
| Pin 19 | GND | (wire twisted with NRFD) | |
| Pin 20 | GND | (wire twisted with NDAC) | |
| Pin 21 | GND | (wire twisted with IFC) | |
| Pin 22 | GND | (wire twisted with SRQ) | |
| Pin 23 | GND | (wire twisted with ATN) | |
| Pin 24 | Logic ground | ||
IEEE 488 is a short-range digital communications 8-bit parallel multi-master interface bus specification. IEEE 488 was created as HP-IB (Hewlett-Packard Interface Bus) and is commonly called GPIB (General Purpose Interface Bus). It has been the subject of several standards.
Although originally created in the late 1960s to connect together automated test equipment, it also had some success during the 1970s and 1980s as a peripheral bus for early microcomputers, notably the Commodore PET. Newer standards have largely replaced IEEE 488 for computer use, but it still sees some use in the test equipment field.
In the late 1960s, Hewlett-Packard (HP) manufactured various automated test and measurement instruments, such as digital multimeters and logic analyzers. They developed the HP Interface Bus (HP-IB) to enable easier interconnection between instruments and controllers (computers and other instruments).
The bus was relatively easy to implement using the technology at the time, using a simple parallel bus and several individual control lines. For example, the HP 59501 Power Supply Programmer and HP 59306A Relay Actuator were both relatively simple HP-IB peripherals implemented only in TTL, using no microprocessor.
HP licensed the HP-IB patents for a nominal fee to other manufacturers. It became known as the General Purpose Interface Bus (GPIB), and became a de facto standard for automated and industrial instrument control. As GPIB became popular, it was formalized by various standards organizations.
In 1975, the IEEE standardized the bus as Standard Digital Interface for Programmable Instrumentation, IEEE 488; it was revised in 1978 (producing IEEE 488-1978). The standard was revised in 1987, and redesignated as IEEE 488.1 (IEEE 488.1-1987). These standards formalized the mechanical, electrical, and basic protocol parameters of GPIB, but said nothing about the format of commands or data.
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