PDP 11/40 M7656 Serial Comms

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PDP 11/40 M7656 Serial Comms	by Bill Degnan - 03/16/2015 08:17
Now that the core system is running again I can turn my attention to adding a display and disk drives to the system. I have a M7856 10 F-C (RS232 WITH 19.2 OPTION?) i.e. serial card and few terminals including a vt52 a LA36 Instructions for booting the PDP 11/40 using RL02 drives http://www.pdp-11.nl/peripherals/disk/rl-info.html Next - I will replace one of the grant continuity cards and put in a M7762 (RL02 controller) in its place and attempt to boot from RL02 using M9312 ROM boot terminator card with RL02 ROM chip installed. I had a hopefully still working RL02 (01) and I bought a second drive from Ian last year (02). I have 10 or so RL02 packs, at least one should be a RT11 boot disk. Reply
M7856 Setup	by Bill Degnan - 03/18/2015 10:48
Using guidance found in documentation and web resources I found the correct pin assignments for a serial console cable to connect from the M7856 to a serial terminal. Fortunately I had a BERG connector available. I set the jumpers to 9600 baud. Click image for larger view. Next I attached the EIN cable end to a null modem adapter and a longer straight-through cable. The end of the straight-through cable was attached to the COMM port of a VT 102 terminal set to 9600 baud. This photo shows the PDP 11/40 with VT-102. I toggled in a program that takes characters typed at the terminal, passes them through the PDP 11/40 and echoes them back to the terminal screen. The progress thus far was short-lived. The system returned to an AC LO failure condition ((see thread))and the 5 amp fuse blew out. I have parts on order so I can make more permanent repairs. But at least I got a little taste of the machine. I should have waited until I finished the power supply repairs but I was impatient, can you blame me? The RAM board was kind of flakey, I need to replace the caps on this card as well as the power supply control board's caps and resistors that have failed. Reply
Downloading programs via serial card	by Bill Degnan - 07/18/2015 14:18
Power supply appears to be fixed after repairs and running for a few hours. We're now back to the point of being able to use a terminal to echo characters. Next, we need to toggle in a bootstrap loader and download the absolute loader into memory. From there we can load BASIC or other programs. Bootstraps Here http://www.psych.usyd.ed.../pdp-11/bootstraps.html Reply