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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 Commodore's 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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