C
C  THIS PROGRAM INITIALIZES AN 8253 INTERVAL TIMER ON AN iSBC 86/12A
C  BOARD TO INTERRUPT THE HOST PROCESSOR EVERY 10 MILLISECONDS.FIRST 
C  THE PROGRAM INITIALIZES THE TIMER AT CONTROL PORT(CONTPT) WITH THE
C  CONTROL WORD(CONTWD) WHICH IS 030H. THIS SELECTS COUNTER 0, READ/LOAD
C  LOW ORDER BYTE THEN HIGH ORDER BYTE, INTERRUPT ON TERMINAL COUNT, AND
C  ACCEPTS COUNT IN BINARY. THE PROGRAM NEXT LOADS THE COUNTER VALUE
C  WITH 10 MILLISECONDS. (THE iSBC 86/12A CLOCK RATE IS 1.23MHZ). THE
C  INTERRUPT ROUTINE(TIMER) RELOADS THE COUNT REGISTER(CNTREG) WITH 10
C  MILLISECONDS, SO THAT AN INTERRUPT IS GENERATED EVERY 10 MILLISECONDS.
C

	PROGRAM PROG3

	INTEGER*1 CONTPT,CONTWD,CNTLOW,CNTHI,CNTREG
	EXTERNAL TIMER

	CALL SETINT (6,TIMER)

	CONTPT = #0D6H
	CONTWD = #030H
	CALL OUTPUT (CONTPT,CONTWD)

	CNTREG = #0D0H
	CNTLOW = #0CH
	CNTHI  = #030H
C
C	LOAD THE LOW ORDER COUNTER BYTE.
C
	CALL OUTPUT (CNTREG,CNTLOW)
C 
C	LOAD THE HIGH ORDER COUNTER BYTE.
C
	CALL OUTPUT (CNTREG,CNTHI)
C
C	ALWAYS TRUE TEST TO CONTINUE INTERRUPTS FOREVER.
C
 5	IF (1.NE.1) GO TO 10
	GO TO 5

 10     END


C
C  THIS SUBROUTINE SERVICES INTERRUPT 6 WHEN IT OCCURS, AND RELOADS
C  THE COUNTER VALUE WITH 10 MILLISECONDS.  TO MAKE THE PROGRAM MORE
C  USEFUL, ADD CODE TO TAKE ACTION BEFORE STARTING THE NEXT INTERVAL
C


$INTERRUPT

	SUBROUTINE TIMER
	INTEGER*1 CNTREG,CNTLOW,CNTHI
 
	CNTREG = #0D0H
	CNTLOW = #0CH
	CNTHI  = #030H

	CALL OUTPUT (CNTREG,CNTLOW)
	CALL OUTPUT (CNTREG,CNTHI)

	RETURN
	END