IC number:	MSM6242B
IC function:	Direct bus connected CMOS real time clock/calendar
Related components:	5C01A (RTC used in 32-bit Amigas)

Component documentation

IC number	Manufacturer	Documentation
MSM6242B	Oki	Datasheet (PDF)

Component versions

IC number	Package	CBM part number	CBM part description
MSM6242B	18-pin DIP	318073-01	RealTime Clock Oki MSM6242B
MSM6242B	24-pin SOP

Positions

Device	Position	Package
A2000	U65	DIP
A2000CR	U801	DIP
A500 Plus	U9	DIP
CDTV	U61	DIP
A501	U9	DIP
A501 Plus	U9 (not installed)	DIP
A601	U9	SOP
PC10-III	U401	DIP

• This RTC is also used on 3rd party A500 or A600 memory expansions and on many A1200 turbo boards.

Pinout DIL package

Pin	Type	Name	Signal name
			A2000	A2000CR	A500 Plus, A501	CDTV	PC10-III
1	Output	STD.P	unused				VCC via R411
2	Input	_CS0	_RES via Q9	GND			RTCLOCKCS'
3	Input	ALE	+5V via Q11	+5V	+5V via R914	+5VD via R95	VCC
4..7	Input	A0..A3	A2..A5			A2..A5 via U59	BADDR0..BADDR3
8	Input	_RD	_CLKRD			_CLKRD via U60, U58 and U74	NIOR'
9	Power	GND	GND
10	Input	_WR	_CLKWR			_CLKWR via U60, U58 and U74	NIOW'
11..14	I/O	D3..D0	PD3..PD0	D0..D3		CD0..CD3	IDATA0..IDATA3
15	Input	CS1	+5V via R150	+5V	+5V via R914	+5VD via R104	VCC
16	Input	XT	connected to OSC2	connected to Y800	connected to Y9	connected to X2	connected to XTAL2
17	Output	_XT
18	Power	VDD	connected to BAT	connected to BT800	connected to BT9	+5VD	connected to BT601

• Note: For the A501 the signal names must be prefixed with X.

Pinout SOP package

Pin	Type	Name
1	Output	STD.P
2	Input	_CS0
3	N/C	NC
4	Input	ALE
5	Input	A0
6	N/C	NC
7	Input	A1
8	N/C	NC
9..10	Input	A2..A3
11	Input	_RD
12	Power	GND
13	Input	_WR
14..16	I/O	D3..D1
17..18	N/C	NC
19	I/O	D0
20	Input	CS1
21	N/C	NC
22	Input	XT
23	Output	_XT
24	Power	VDD