Minimig RTC

Real time clock that keeps the time over power cycling.
Advantages:

• Disc files get correct date
• Any software dependent on date will work correctly (astronomy/satellite?)

Commodore: A501 Rev5, 512k + RTC

RAM organised as 16 x (Sanyo LM33256G-12 DIP16) 1 x 256kbit Dynamic RAM

RTC 5 Volt "OKI M6242B" U9 DIP18 clocked with a 32768 Hz crystal, backed up by a 3,6V NiCd battery

M6242B datasheet

Register table:

Address Input	Register name	Data				Count value	Description
		D3	D2	D1	D0
0	S1	S8	S4	S2	S1	0-9	1-second digit register
1	S10	*	S40	S20	S10	0-5	10-second digit register
2	MI1	mi8	mi4	mi2	mi1	0-9	1-minute digit register
3	MI10	*	mi40	mi20	mi10	0-5	10-minute digit register
4	H1	h8	h4	h2	h1	0-9	1-hour digit register
5	H10	*	PM/AM	h20	h10	0-2 or 0-1	PM/AM 10-hour digit register
6	D1	d8	d4	d2	d1	0-9	1-day digit register
7	D10	*	*	d20	d10	0-3	10-day digit register
8	MO1	mo8	mo4	mo2	mo1	0-9	1-month digit register
9	MO10	*	*	*	MO10	0-1	10-month digit register
A	Y1	y8	y4	y2	y1	0-9	1-year digit register
B	Y10	y80	y40	y20	y10	0-9	10-year digit register
C	W	*	w4	w2	w1	0-6	Week register (0=Sunday)
D	CD	30 sec. ADJ	IRQ FLAG	BUSY	HOLD	-	Control Register D
E	CE	t1	t0	ITRPT /STND	MASK	-	Control Register E
F	CF	TEST	24/12	STOP	REST	-	Control Register F

REST = RESET

ITRPT/STND = INTERRUPT/STANDARD

Note 1) Bit * does not exist (unrecognized during a write and held at "0" during a read).

Note 2) Be sure to mask the AM/PM bit when processing 10's of hour's data.

Note 3) BUSY bit is read only. The IRQ FLAG bit can only be set to a "0". Setting the IRQ FLAG to a "1" is done by hardware.

Note 4) PM at 1 and AM at 0 for PM / AM bit.

Micronik: Realtime Clock for Clockport, RTC

Pin maps:

MCU pins

FPGA pins