Specifications

Application Examples
;***********************************************************
;* *
;* PROCEDURES *
;* *
;***********************************************************
;
;
INIT_PIC PROC ;
; THIS PROCEDURE IS CALLED TO INITIALIZE THE 8259A PIC.
; THE PIC IS INITIALIZED TO: SINGLE MODE, EDGE TRIG-
; GERED, INTERRUPT TYPES8-15DFORIRQS 0-7 RE-
; SPECTIVELY, 8088 MODE, NORMAL (NON-SPECIFIC) END-
; OF-INTERRUPT, IRQ LINES 0-7 ENABLED.
;
MOV DX,PORT_A_8809A ; ADDRESS THE FIRST BYTE
MOV AL,ICW1_8809A ; WRITE 1ST ICW
OUT DX,AL ; OUTPUT 1ST ICW
MOV DX,PORT_B_8809A
MOV AL,ICW2_8809A
OUT DX,AL ; WRITE 2ND ICW
MOV AL,ICW3_8809A
OUT DX,AL ; WRITE 3RD ICW
MOV AL,ICW4_8809A ; WRITE 4TH ICW
OUT DX,AL ; OUTPUT 4TH ICW
MOV AL,OCW1_8809A ; WRITE OCW1 (ASSUMES
; STD DOS USE)
OUT DX,AL ; OUTPUT MASK
RET
INIT_PIC ENDP
;
;
INIT_TMR2 PROC
;
; THIS PROCEDURE IS CALLED TO INITIALIZE THE COUNTER/TIMER 2
; IN THE 8254. ONLY TIMER 2 WILL BE USED AS A RATE
; GENERATOR, IDENTICAL TO THE WAY STD DOS USES IT.
; THE INTERRUPT WILL OCCUR ONCE EVERY 55 MSEC.
;
; INPUTS: NONE
; OUTPUTS: NONE
; CALLS: NONE
; DESTROYS:
;
MOV AX,TMR2_MODE2 ; INITIALIZE TIMER 2
PUT CNTRL_WORD ; FOR MODE 2
MOV AL,0 ; FREQUENCY = MINIMUM
PUT TIMER2 ; SEND LEAST SIG BYTE FIRST
PUT TIMER2 ; SEND MOST SIG BYTE
RET
;
INIT_TMR2 ENDP
;
4-11