A Made IT project


IEEE 488

An HP bidirectional parallel printer interface capable of handling 15 devices @ 500 kBps.
The maximum distance = number of devices * 2 meters with an absolute maximum of 20 meter.

The above specifications seem confusing (and they are), but it is the most accurate documentation we have!

The bus consists of one controller and 1 to 15 devices in a daisy chain fashion shown in the picture below:

Bus Structure

An IEEE 488 device has per device 4 different addresses for Command, Listen, Talk and Secondary. Let's say we have a plotter on address 0 then his addresses would be:

Amphenol 24 pins male Amphenol 24 pins female
1Data Bit 1DIO1Talker
2Data Bit 2DIO2Talker
3Data Bit 3DIO3Talker
4Data Bit 4DIO4Talker
5End Or IndentityEOITalker/Controller
6Data ValidDAVController
7Not Ready For DataNRFDListener
8No Data AcceptedNDACListener
9Interface ClearIFCController
10Service RequestSRQTalker
12Shield -
13Data Bit 5DIO5Talker
14Data Bit 6DIO6Talker
15Data Bit 7DIO7Talker
16Data Bit 8DIO8Talker
17Remote EnabledRENController
18Ground DAV -
19Ground NRFD -
20Ground NDAC -
21Ground IFC -
22Ground SRQ -
23Ground ATN -
24Logical Ground -

Technical Description
The bus is TTL active low (open collector). Every device which asserts a signal low will override the high from another device.