Page 164 - Digital Electronics by harish

RIM (Read Interrupt Mask)

This instruction is used to read the status of RST 7.5, RST 6.5 and RST
5.5 interrupts like pending and enable / disable details. This instruction is also
used for reading the serial data. When the RIM instruction is given, the
microprocessor loads the details into the accumulator.

Figure 5.18 : Bits used in RIM instruction

Bits D6, D5 and D4 give the pending details of RST 7.5, RST 6.5 and
RST 5.5 interrupts respectively. Bits D2, D1 and D0 give the masked /
unmasked details of RST 7.5, RST 6.5 and RST 5.5 interrupts respectively. Bit
D3 gives the status of Interrupt enable Flip-flop.

Example :
Suppose after the execution of RIM instruction, the accumulator has 49H. The
meanings are:

Figure 5.19 : Example for RIM instruction

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