This is the logic analyzer showing the failure of program counter (PC) incrementing on the PC11 R211 card. Run is the run flip flop output which the falling edge when the machine halts was used to trigger the capture. IR is the 3 bit instruction register which shows what instructions are executing. The start of each instruction is when the fetch signal goes high. PC is the program counter. The two deposit and clear accumulator (DCA) instructions are the end of setting up the instructions at 1177 and 1200. At 0325 it executes a jump (JMP) to 1177. It then executes a interrupt on I/O transfer (IOT) at 1177. It next should have executed the next sequential instruction at 1200 (octal). Instead it executed a halt operate (OPR) instruction at 1000 since the carry into PC bit 4 did not occur. Pc4inc is the signal that should have caused the increment. This indicates the R211 card has a failure.
The IOT 00 is the execution of the interrupt on. The int ack, dly, and en signals are part of the logic enabling interrupts. The test uses an interrupt to capture the actual location the jump subroutine (JMS) that should have executed after the IOT jumps to. Run stop is the signal that halts the processor. The first signal Clk1 is a clock for the analyzer which isn't connected.
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