Ugh, PC0 + PDP-8I problem. - test-drb@ccmp.vtda.org

24 Nov 1999

I have just started to look at this problem but I don't like it already.

Here we go:

If I load a RIM paper tape into my 8I using (single step) it loads in fine.

If I load in a RIM paper tape into my 8I running (no manual steps).. the
data loaded is garbage , and may not even be in the right place.

If I toggle in a program to test the "all 1s" paper tape it passes (both
single step and running)

If I toggle in a program to test the "all 0s" paper tape it passes (both
single step and running)

If I toggle in a *larger* program to read a "1s and 0s paper tape" it passes
(both single step and running). [this is ones and zeros alternating]

I have checked the strobe line with my scope at it appears normal.

I have checked and re-aligned the paper tape reader and data coming out of
it (in step mode) is okay.

My next move will be to try and load 32 bytes from the paper tape reader
into core (not the RIM loader, my own quick program).

and

Write a quick program to write various numbers to core and make sure the are
written correctly.

There are no other devices connected.

It could be the data is improperly strobed at high speed (adjacent holes on
either side of the actual byte being read in are allowing enough light
through to trigger the photo detector).

I have the gain up quite a bit to strobe the feed hole.... but not enough to
screw up the above three tests.

Any suggestions????????????????

john