The 8051 Microcontroller and Embedded

Department of Computer Scien

ce and Information Engineering

National Cheng Kung University, TAIWAN

HANEL

OTHER MODES OF THE 82558255 in Mode 1:

I/O With Handshaking

Capability

(cont

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¾INTEa (interrupt enable for port A)
ƒThe 8255 can disable INTRa to prevent it if from interrupting the CPUƒIt is internal flip-plop designed to mask INTRaƒIt can be set or reset through port C in BSR mode since the INTEa flip-flop is controlled through PC6ƒINTEb is controlled by PC2 in BSR mode
¾Status word
ƒ8255 enables monitoring of the status of signals INTR, OBF, and INTE for both ports A and BƒThis is done by reading port C into accumulator and testing the bitsƒThis feature allows the implementation of polling instead of a hardware interrupt