rtc.z80

; Basic driver for TI BQ4845 RTC
; Register definitions
.SEC:		equ RTCBASE + 0x00	; Seconds
.SECALM:	equ RTCBASE + 0x01	; Seconds alarm
.MIN:		equ RTCBASE + 0x02	; Minutes
.MINALM:	equ RTCBASE + 0x03	; Minutes alarm
.HR:		equ RTCBASE + 0x04	; Hours
.HRALM:		equ RTCBASE + 0x05	; Hours alarm
.DAY:		equ RTCBASE + 0x06	; Day
.DAYALM:	equ RTCBASE + 0x07	; Day alarm
.DOW:		equ RTCBASE + 0x08	; Day of week
.MTH:		equ RTCBASE + 0x09	; Month
.YR:		equ RTCBASE + 0x0A	; Year
.RATES:		equ RTCBASE + 0x0B	; Programmable rates
.IE:		equ RTCBASE + 0x0C	; Interrupt enables
.FLGS:		equ RTCBASE + 0x0D	; Flags
.CTRL:		equ RTCBASE + 0x0E	; Control
.UNSD:		equ RTCBASE + 0x0F	; Unused

SetUpdateInhibit:
	ld a, 00001110b
	out (.CTRL), a
	ret

UnsetUpdateInhibit:
	ld a, 00000110b
	out (.CTRL), a
	ret

SetPeriodicIntRate:
	and 00001111b		; Mask off non-rate bits
	out (.RATES), a
	ret

EnablePeriodicInt:
	ld a, 00000100b
	out (.IE), a
	ret

DisablePeriodicInt:
	ld a, 00000000b
	out (.IE), a
	ret

SetRTC:
	call		SetUpdateInhibit
	ld		a, b
	out		(.SEC), a
	ld		a, c
	out		(.MIN), a
	ld		a, d
	out		(.HR), a
	ld		a, e
	out		(.DAY), a
	ld		a, h
	out		(.MTH), a
	ld		a, l
	out		(.YR), a
	call		UnsetUpdateInhibit
	ret

GetRTC:
	call		SetUpdateInhibit
	in		a, (.SEC)	; Read seconds
	ld		b, a
	in		a, (.MIN)	; Read minutes
	ld		c, a
	in		a, (.HR)	; Read hours
	ld		d, a
	in		a, (.DAY)	; Read day
	ld		e, a
	in		a, (.MTH)	; Read month
	ld		h, a
	in		a, (.YR)	; Read year
	ld		l, a
	call		UnsetUpdateInhibit
	ret