The problem is that the 11/05 CPU has a (sort of) serial console built in. So if you
install an M7856 that is also set as the default console CSR you'll have problems.
For test purposes I'd set up an M7856 (with the LTC disabled) at an alternate address
and try a simple (toggled in) test program to see if you can get any output to it.
As I recall there were (at least) 3 different revs of the 11/05 (or 11/10) CPU boards.
The last rev, allowed you to disable the built-in SLU (the best option IMHO) and use a
*real* SLU. Part of the problem is that the SLU on the CPU was pretty flakey. Rather
than use a crystal to generate the frequency they used a multivibrator set up which caused
the frequency to be all over the place. One of the CPU variants allowed an external clock
generator to be used. The M9970 I believe also brought out all of the TTL levels so one
thought is to cable up an external board that has RS232 drivers and a (crystal based) baud
rate generator. It should give better results than just doing what's internal. I
gave up on that idea once I found out I could disable it on my CPU board set.
TTFN - Guy
On Sep 3, 2010, at 7:59 AM, Bill Degnan wrote:
We have been working to establish some sort of I/O,
preferably RS232 with a
PDP 11/05
After spending many hours on the problem we came up empty.
The computer itself appears to be OK, the continuity cards are in the right
places, the core RAM works, simple test programs function properly. For
example entering code from 177700: 000240 000777 the computer will set the
lowest address bit to 0-1-0-1 continuously.
The current configuration is
M9970
M7260
M7261
M920/H214
G110
G231
Grant
UNIBUS bridge
M7856
Grant
Grant
We don't have a device for 20ma current loop-ing so we're trying to use the
M7856 for RS232 communications. We're not sure what ports to use with the
M7856 while a M9970 is also installed, does a conflict exist?
We have found the following resources and worked through what info was
provided there
http://www.shiresoft.com/pdp-11/11-10/index.html
http://www.pdp-11.nl/per...terface/dl11w-info.html
http://www.bitsavers.org...-DL11W-OP-001_May77.pdf
If anyone on this list can assist with diagnostic steps it would be greatly
appreciated. For example an octal listing for a character echo program.
Please contact me directly. We're not sure what port to use for RS232, the
default teletype port seems to be 60. I think we're close, and it's also
possible that there is a problem with the card. The switch settings appear
to be OK.
Thanks
Bill Degnan