Re: HP 9825 A & HP 9872 B

Paul Berger

1,2,3,4,13,14,15,&16 are the data lines 6 is DAV (Data Valid) and when there is data on the bus it sould go low DAV along with NRFD (7) and NDAC (8) are the handshake signals.   Your plotter should take NRFD high when it is idle and NDAC should be low.  The 9825 will put data on the bus and then take DAV low the plotter will take NRFD low and NDAC high to acknowledge the data ...  See page 23 of the 98034 manual.


On 2020-04-30 1:28 p.m., David Stokes wrote:
Hello again, and thanks to everyone for setting me in the right direction. I used a logic probe this morning, and found signals on pins 6, 13, 14, 15 & 16 when I sent the pen# 2 command.  I believe 6 is a Data Handshake, and 13 - 16 are the corresponding data lines, so at least this indicates some activity in the 98034, though whether these outputs are correct I cannot say.

I attempted a plotter self test using the service manual for an HP 9872 A, but after pressing Reset and Step nothing happened, according to the LEDs the Self Test did not proceed.  Does anyone have a copy of the 9872 B Self Test procedure, as I have been unable to find it online.

Thanks in advance, and best regards,  David.

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