More 11/45

Tony wrote.... Did that today. LTC is going through the schmitt trigger just fine. The diag no longer fails on "bit 7 stuck in LTC". Instead, it now locks up at the same spot in the DL11-W diag as the other two DL11-W cards. Right after "01 devices under test", the machine just halts with the cursor still at the end of that line. Agreed. Greaaaat :\ Here's where I'm trying to start. I was looking at some of the code on this website, hints for troubleshooting a dead PDP11. It's at: http://www.psych.usyd.edu.au/pdp-11/hints.html I enter and run the Line Time Clock Interrupt test from that webpage, and the system halts at location 4. How on earth? Does the 11/45 have some interrupts to specific locations for things like power fail or something? Should a unexpected trap to location 4 mean something special to me? Here is the section from that website reproduced below: ------- Line Time Clock Interrupt Test Most of the older PDP11's had a line time clock that would interrupt at mains frequency (50 or 60Hz). On early LSI-11's, it was not programmable but enabled by a switch on the front panel. Load the following program (which is just a trap catcher and interrupt enable), and start. If an early LSI-11's, substitute 000240 for the lines marked #, run the program for a second or two, then enable the clock. The program should halt at address 104 (the interrupt vector address is 100, and the vector is loaded with 102, which then executes a halt at 102, the PC will then be 104). Location Contents Opcode Comment 001000 012706 mov #770,sp set the stack pointer 001002 000770 001004 005000 clr r0 memory pointer 001006 012701 mov #2,r1 trap value 001010 000002 001012 010120 loop: mov r1,(r0)+ set trap vector value 001014 005020 clr (r0)+ set halt instruction in trap 001016 062701 add #4,r1 update r1 for next trap 001020 000004 001022 020600 cmp sp,r0 load up to stack pointer 001024 001372 bne loop # 001026 012737 mov #100,@#ltc enable clock interrupt # 001030 000100 # 001032 177546 001034 000777 br . loop for ever If the processor doesn't halt, then your clock isn't running. If it halts at 6, then the clock register is missing. ---------- I also wanted to run the trap catcher program from that website to help test software traps & interrupts. However, I don't understand part of what they say to do. I can certainly enter the program, but then they say to deposit 777 into loc 1000. That would overwrite the first word of the program. Not sure what they want done there or I'd run that to see what it comes up with. Any thoughts? Jay West