AMD Am186 Series, Instruction Set

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Instruction Set 4-252
XOR XOR
Examples
This example turns on Timer 2 by setting the Enable (EN) and Inhibit (INH) bits in the
Timer 2 Mode and Control (T2CON) register.
This example procedure turns an LED on or off by toggling the signal level of programmable
I/O (PIO) pin 3 in the PIO Data 0 (PDATA0) register.
Tips
To clear a register to 0, use XOR to exclusive OR the register with itself.
Related Instructions
If you want to See
Clear particular bits of a component to 0 AND
Toggle all bits of a component NOT
Set particular bits of a component to 1 OR
TMR2_CNT_ON EQU 0C000h ; mask for enable & inhibit bits
; turn on Timer 2
MOV DX,TMR2_CTL_ADDR ; address of T2CON register
IN AX,DX ; read T2CON into AX
XOR AX,TMR2_CTL_ON ; set enable & inhibit bits
OUT DX,AX ; write AX to T2CON
PIO3_MASK EQU 0008h ; PDATA0 bit 3
; toggle PDATA0 bit 3
TOGGLE_PIO3 PROC NEAR
; save registers
PUSH AX
PUSH DX
MOV DX,PIO_DATA0_ADDR ; address of PDATA0 register
IN AX,DX ; read PDATA0 into AX
XOR AX,PIO3_MASK ; toggle bit 3
OUT DX,AX ; write AX to PDATA0
; restore saved registers
POP DX
POP AX
RET
TOGGLE_PIO3 ENDP