; clock module 4/5/83 goodall
; this module contains routines which know about the counter
; timer hardware in the system

cgroup	group	code,data

	public	clock_init	; used by init:
	public	clock_baudset	; used by serial_init:
;************************************************************************
;*									*
;*	        8253 COUNTER TIMER PORT AND DATA EQUATES		*
;* 		4/7/83 dwg						*
;************************************************************************

timer_0_reg	equ	48h		; keyboard 1200 baud
timer_1_reg	equ	4ah		; rs232-baud	
timer_2_reg	equ	4ch		; tick
	
timer_cmd_reg	equ	4eh		; "

timer_60_hz	equ	19886		;constant for 60.001 hz tick
timer_1000_hz	equ	533h		;constant for 1000 hz tone

sel_ctr_0	equ	0		; select counter 0
sel_ctr_1	equ	1		; select counter 1
sel_ctr_2	equ	2		; select counter 2

ctr_latch	equ	0		; counter latching
rl_msb_only	equ	2		; read/load msb only
rl_lsb_only	equ	1		; read/load lsb only
rl_lsb_msb	equ	3		; read/load lsb, msb

mode_0		equ	0		; int on term count
mode_1		equ	2		; pgmable one shot
mode_2		equ	4		; rate generator
mode_3		equ	6		; square wave generator
mode_4		equ	8		; software triggered strobe
mode_5		equ	9		; hardware triggered strobe

binary		equ	0		; binary counter 16 bits
bcd		equ	1		; bcd counter ( 4 decades )

; CLOCK SPEED DEFINITIONS FOR OLYMPIA PEOPLE

BAUD_RATE	EQU	1200*16
CLOCK		EQU	49152	; 4915.2 KHz
BAUD		EQU	CLOCK/2/(BAUD_RATE/100)
RTCLK		EQU	BAUD_RATE/20
	eject

	cseg

; initialize tick period from factor in ram location
clock_init:
	mov	al,sel_ctr_2 + rl_lsb_msb + mode_3 + binary
	out	timer_cmd_reg,al; select appropriate counter
	mov	ax,rtclk	; get interval init (16 bits)
	out	timer_2_reg,al
	mov	al,ah		; al = high byte of init value
	out	timer_2_reg,al
	ret

; set serial baud rate per caller's ax
clock_baudset:
	push ax				; save caller's baud rate
	mov al,76h ! out timer_cmd_reg,al	
	pop ax				; restore caller's baud rate
	out timer_1_reg,al		; set low order baud factor
	mov al,ah
	out timer_1_reg,al		; set high order baud factor 
	ret				; return to caller

	dseg
	db	0
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