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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
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.