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assemblyintel-8080

Intel 8080 Instruction at OP Code 0x20 and 0x30

According to Intel's 8080-8085 Assembly Language Programming guide, the OP Code 20 corresponds to the Read Interrupt Mask (RIM) instruction, and 30 corresponds to the Set Interrupt Mask (SIM) instruction.

instructions

However, only the 8085 has the RST5.5, RST6.5, and RST7.5 hardware interrupts. Are the instructions at 0x20 and 0x30 just NOP on 8080 hardware?

Solution

  • The 8085 has 2 instruction functions:

    • To read and set the interrupt mask.
    • To communicate via serial port interface.

    On 8080, these opcodes are NOPs.