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Status Panel

The WAIT lamp illuminates when a WAIT signal is present in any of the 16 channels.

The INT lamp monitors all 16 Interrupt signals feeding the Interrupt Controller circuit. The lamp remains illuminated as long as one interrupt signal at least is present. This is true even if interrupts are disabled by either software or hardware.

The IE lamp monitors the Interrupt Enable flag. It illuminates if interrupts are enabled by software. Similarly, the TE lamps indicates whether Trap is enable.

Lamps C, Z, N, V monitor the flags: Carry, Zero, Negative, Overflow (respectively) from the flag register.

The IRQ (Interrupts Request) switch, when inactive (down), prevents the Interrupt signals from reaching the Interrupt circuit causing the CPU to ignore all interrupts even if those are enabled by software. The Interrupt Enabled (IE) flag is not affected by this switch.

The TRAP switch enables/disables "traps". When a fail condition occurs, if trap is enable by software and the TRAP switch is active (up), a trap routine is called automatically.

The BP (Halt on Break Point) switch, when active (up), causes the computer to halt when the program counter reaches a certain address previously set by the operator. We cover this later in this section.

Lamp FAIL illuminates when the CPU recognizes a Fail condition and remains in that state until the operator clears the condition explicitly by pressing the CLR button.

The HOF (Halt On Fail) switch, when active (up), causes the CPU to halt as soon as a fail condition occurs. This is useful for debugging.

The RESET button fires the Master Reset signal causing all CPU registers to clear up. The signal is also spread throughout all I/O channels to clear peripheral circuitry as well.

PWD lamp indicates that the Power Supply is on. The Power switch turns the Power Supply on or off.