Programming instructions

INPUT- OUTPUT STATUS INSTRUCTION

The iors (in-out read status) instruction, 700314, enables the status of all

IO devices to be read into the AC and sampled. Various IO device states

are indicated by the presence of a 1 or 0 in the bit positions allocated for

that device (see Figure 9).

Program Interrupt On

Tape Reader Flag

Tape Punch Flag

Keyboard Input Flag

Card Punch Malfunction

Type-Out Flag

Card Punch Row Flag

Display Flag Card Reader End of File Switch

Clock Overflow Flag Card Reader Malfunction

Clock Enabled

Magnetic Tape Interrupt

x = Program Interrupt Connected

Figure 9 - Input-Output Status instruction, bit assignment

CLOCK/TIMER

The Clock produces a pulse every l/60 second (16.6 milliseconds) which

temporarily interrupts the program (in the same manner as the data

interrupt) and a 1 is added to the contents of memory cell 7 using 2’s

complement addition. If the contents of memory cell 7 are 0 after the

addition, the Clock flag is set to 1, which initiates a Program Interrupt if

the Interrupt is on. Depressing the START key on the Operator Console

clears the Clock flag and disables the Clock. The iot instructions associated

with the Clock are:

csf - 700001 - Skip the next instruction if the Clock flag is a 1

cof - 700004 - Disable the Clock and clear the Clock flag

con - 700044 - Enable the Clock and clear the Clock flag

may be examined or modified. By presetting register 7 to a number, a

Program Interrupt will occur when the register overflows after a timed

interval.