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Data and Execution Control Panel

The two 12-lamps displays ADDR and DATA read from Memory or registers depending of the selection made in section Display Source Panel.

When reading from Memory, the DATA display reads the memory location which address is shown in display ADDR. If the computer is halted, the Operator can set this address by entering its value in the Entry Switches, then pressing the SET button near the ADDR display. As soon as the button is pressed, both ADDR and DATA displays change to reflect that address and its memory content.

The address can be also incremented or decremented by pressing buttons ">" or "<" respectively. Once the button is preset, both displays are automatically updated.

When a register or channel is selected (instead of M) in the Display Source panel, the ADDR display continues to show memory addresses, either in halt or normal program execution modes.

Button STO (store) allows to over-write content to either memory, register or channel (as selected in the Display Source section). When pressed, the content in the Entry Switches are copied to the selected register, the selected channel, or the memory cell which address is currently in the ADDR display.

Button HTL (halt) halts the machine. The button illuminated to indicate such condition.

Button RUN cause the machine to enter normal program execution mode. Program starts from the address currently stored in the Program Counter register. The button illuminates to indicate such condition.

Buttons SET, <, >, STO are disabled automatically during normal program execution.

If the STEP switch is in its active position (up), the computer will halt after completing the next instruction cycle. Pressing the RUN button repeatedly allows to run the program one instruction at the time.

To resume running the program normally, down the STEP switch, then press the RUN button.

If the switch is soddenly activated (up) during normal program execution, the computer will halt once the current instruction cycle is completed, entering single-step execution mode.

A Break Point is a memory address set by the Operator so when the program reaches it, the machine halts automatically. This is useful for debugging.

If the switch BP (Halt on Break Point) is active (up) in the Status panel, program execution will stop as soon as the Program Counter reaches the break point; the instruction at that address will not be executed. Pressing the RUN button again will resume program execution, but if the same address is reached again, the machine will halt again. If you place a break point in the middle of a loop, for example, you will be able to execute the loop one iteration at the time.

The switch "BP/M" allows the operator to select what the ADDR display is actually reading; that could be either Break Point (up) or Memory (down). When in the BP position, pressing the SET button causes the Entry Switches content to be set as the "Break Point" address.

During normal program execution, the Operator can operate the BP/M switch to dynamically change the ADDR display reading between Break Point and memory address.