IEEE-488 allows up to 15 devices to share a single bus by daisy-chaining. The maximum data rate is about one megabyte per second. The 16 signal lines within the passive interconnecting HP-IB cable are grouped into three clusters according to their functions: Data Bus, Data Byte Transfer Control Bus, and General Interface Management Bus.
| Pin | Name | Description | Source |
|---|---|---|---|
| 1 | DIO1 | Data Bit 1 | Talker |
| 2 | DIO2 | Data Bit 2 | Talker |
| 3 | DIO3 | Data Bit 3 | Talker |
| 4 | DIO4 | Data Bit 4 | Talker |
| 5 | EOI | End Or Indentity | Talker/Controller |
| 6 | DAV | Data Valid | Controller |
| 7 | NRFD | Not Ready For Data | Listener |
| 8 | NDAC | No Data Accepted | Listener |
| 9 | IFC | Interface Clear | Controller |
| 10 | SRQ | Service Request | Talker |
| 11 | ATN | Attention | Controller |
| 12 | Shield | - | |
| 13 | DIO5 | Data Bit 5 | Talker |
| 14 | DIO6 | Data Bit 6 | Talker |
| 15 | DIO7 | Data Bit 7 | Talker |
| 16 | DIO8 | Data Bit 8 | Talker |
| 17 | REN | Remote Enabled | Controller |
| 18 | Ground DAV | - | |
| 19 | Ground NRFD | - | |
| 20 | Ground NDAC | - | |
| 21 | Ground IFC | - | |
| 22 | Ground SRQ | - | |
| 23 | Ground ATN | - | |
| 24 | Logical Ground | - |
Data Lines:
| Name | Description |
|---|---|
| DIO1 to DIO8 | Data Input Output |
Handshake Lines:
| Name | Description |
|---|---|
| DAV | Data Valid |
| NRFD | Not Ready For Data |
| NDAC | Not Data Accepted |
Interface Management Lines:
| Name | Description |
|---|---|
| ATN | Attention |
| IFC | Interface Clear |
| REN | Remote Enable |
| SRQ | Service Request |
| EOI | End or Identify |
Some ancient computers used this bus widely: the Commodore PET/CBM range of educational/home/personal computers, whose disk drives, printers, modems, etc, were daisy-chain connected to the (host) computer, talking and listening on the designated bus lines to perform their jobs. All of Commodores post-PET/CBM 8-bit machines, from the VIC-20 to the C128, utilized a proprietary serial IEEE-488 for peripherals, with round DIN connectors instead of the heavy-duty HP-IB plugs. Several manufacturers used IEEE-488 as a peripheral interface to connect disk drives, tape drives, printers, plotters and advanced pocket calculators to their workstation products.
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