HPIB Probe

A HPIB probe interface made as a quicky to debug HPIB trouble.

It uses the HP 01650-63203 isolation adapter which uses a 2x20 pin connector which is easier to put on a board, and it contains the termination network.

The device’s pin assignments are as follows:

The “ADDR” label is strange here, but it is required to exist for the inverse assembler to work. It just has a dummy assignment to an unused pod.

The STAT field has the following signal assignments:

Bit	Signal
0	ATN
1	EOI
2	REN
3	IFC
4	SRQ
5	NDAC
6	DAV
7	NRFD

The DAV signal is also used as the J clock signal on the analyzer pod.

The combination of ATN and EOI comes out on a separate pin on the device. This should be connected to the K clock of the next pod. The analyzer clocks should be J down OR K down.

Example trace

I connected my HP 5385A frequency counter to my HP 9825A calculator and wrote a simple loop to read the ID of the counter:

dev "meas",703
wrt "meas","ID"
red "mes",X
dsp X
gto 1

A similar program for the HP 85A would be:

10 output 703,"ID"
20 enter 703;V
30 disp "type: ";V
40 goto 10

An example trace from the 1st program looks as follows:

It starts by sending a COMMAND LAG_03. This makes device 3 the LISTENER (the 5384).

It then sends the ID string as data to that device. This will make that device want to answer its type number. It now sends the COMMAND LAG_21 making device 21 the listener (the 9825A) and device 3 the TALKER (by sending the TAG_03) command. Device 3 now answers HP5385A. The final command is UNLISTEN which cleans the listener. The set then repeats.

Problem solving HPDISK communication

I built the HPDISK device (see http://www.dalton.ax/hpdisk/). But it would not work on neither my HP 85A nor my 9825A. It looked like something was wrong with HPIB communications.

I made a HPIB trace of the HP85A command:

cat ":D700"

which looked like this:

This repeatedly does a parallel poll. That parallel poll should have been answered by the HPDISK device by pulling bit 0 of the data lines LOW. This does not happen, and that does seem to be at least the first cause.

After the poll it UNLISTENs and UNTALKs; the other commands I do not yet know 😉

Another try delivered this:

More info on HP-IB: