cc65/libsrc/cbm610/systime.s

;
; Stefan Haubenthal, 2009-07-27
; Ullrich von Bassewitz, 2009-09-24
;
; time_t _systime (void);
; /* Similar to time(), but:
;  *   - Is not ISO C
;  *   - Does not take the additional pointer
;  *   - Does not set errno when returning -1
;  */
;

        .include        "time.inc"
        .include        "cbm610.inc"
	.include 	"extzp.inc"

	.import		sys_bank, restore_bank
	.importzp	tmp1, tmp2


;----------------------------------------------------------------------------
.code

.proc	__systime

; Switch to the system bank

	jsr	sys_bank

; Read the clock

 	ldy	#CIA::TODHR
	lda	(cia),y
	bpl	AM
	and	#%01111111
	sed
	clc
	adc	#$12
	cld
AM:	jsr	BCD2dec
	sta	TM + tm::tm_hour
	ldy	#CIA::TODMIN
	lda	(cia),y
	jsr	BCD2dec
	sta	TM + tm::tm_min
	ldy	#CIA::TODSEC
	lda	(cia),y
	jsr	BCD2dec
	sta	TM + tm::tm_sec
	ldy	#CIA::TOD10
	lda	(cia),y			; Dummy read to unfreeze

; Restore the bank

	jsr	restore_bank

; Convert to a time

  	lda	#<TM
  	ldx	#>TM
  	jmp	_mktime

.endproc

;----------------------------------------------------------------------------
; dec = (((BCD>>4)*10) + (BCD&0xf))

.proc	BCD2dec

	tax
  	and    	#%00001111
  	sta    	tmp1
  	txa
        and     #%11110000      ; *16
        lsr                     ; *8
        sta     tmp2
        lsr
        lsr                     ; *2
        adc     tmp2            ; = *10
        adc     tmp1
        rts

.endproc

;----------------------------------------------------------------------------
; TM struct with date set to 1970-01-01
.data

TM:    	.word           0       ; tm_sec
        .word           0       ; tm_min
        .word           0       ; tm_hour
        .word           1       ; tm_mday
        .word           0       ; tm_mon
        .word           70      ; tm_year
        .word           0       ; tm_wday
        .word           0       ; tm_yday
        .word           0       ; tm_isdst