pdp11/34 Programmers' Console

    One of the (many) options that DEC offered on the pdp11/34 was the programmers' console. This was an attempt to replace the "lights and switches" that many programmers, and technicians, had come to love (or hate, depending on perspective) over the years. It was a radical departure from traditional minicomputer consoles in its design.

    Instead of having individual switches and indicator lamps, the 11/34 panel used a six digit 7-segment display for data and address, and six individual LEDs for RUN, SR DISP, BUS ERR, DC ON, and BATT functions. I'll describe each of these functions in turn.

    The seven segment calculator-style readout on the panel is used for address, data, and switch register display, depending on the current context of the system.

    In a typical operation of writing a data word to an (arbitrary) address, the operator would enter the desired address into the keyboard and depress the LAD (Load ADdress) button. This would instruct the machine to get ready to receive a data word and show the just input address on the display. At this point the operator would enter the desired data word on the keypad and press the DEP (DEPosit) button which would store the datum into the CPU's memory. The display would be updated to show the data word. To continue depositing data into subsequent sequential locations, the operator would enter the data words into the keypad and press the DEP button for each word. Examining memory contents was substantially similar; the operator would input the desired address on the keypad, hit the LAD key (the display would show the address), then press the EXAM (EXAMine) button to show the datum at that address.

    The SR DISP light indicated that the display was showing the contents of the switch register which in machines with conventional panels reflected the data switches at all times. The SR (accessable in the -11 at address 777570) was "loaded" by inputting the desired datum on the keypad and pressing the LSR (Load Switch Register) key.

    The BUS ERR indicator reflected error status on the UNIBUS, including non-existant addresses and parity errors. The MAINT lamp showed that the CPU was in "maintenance" mode which allowed certain operations that were illegal under normal operation to occur; like deliberately writing bad parity to memory.

    The "control" group of keys include INIT, START, BOOT, CONT, and HLT/SS. There is a "CNTRL" key that acts as a "safety" on these buttons, most of which are self-explanatory.

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