8701 / 7701 clock generator pinout

DIP-16. Dot clock and color clock from one crystal (later C64 boards, C128)

Crystal oscillator and divider in 16 pins. The crystal frequency, buffered, is the color clock on pin 8 (14.31818 MHz NTSC, 17.734472 MHz PAL); the dot clock for the VIC-II leaves on pin 6 (8.18 MHz NTSC, 7.88 MHz PAL). Pin 7 picks the divider: open for NTSC, tied LOW for PAL (jumper J2 or J3 on the board). It replaces the 74LS629 clock circuit of the early C64 boards. The 250425 parts list gives the 7701 and the 8701 one Commodore part number (251527-01). No clock on pin 6 means no picture and a dead CPU, because the VIC-II makes the CPU clock from it.

Open the interactive 8701 pinout

Pins

Pin	Name	Type	Signal
1	NC	nc	No connection.
2	VSS	ground	0 V.
3	NC	nc	No connection.
4	NC	nc	No connection. The C64C schematics tie it to ground.
5	/RESET	ctrl	Reset, active LOW, for testing only: held LOW it resets and stops the frequency divider. It has a weak internal pull-up, so in normal use it is tied HIGH or left open (Commodore drawing 251527-01 sheet 1). The C64C schematics do not draw this pin. UNVERIFIED
6	DOT	clock	Dot clock out to the VIC-II: 8.18 MHz NTSC, 7.88 MHz PAL.
7	/PAL	ctrl	Video standard select. Open = NTSC; LOW = PAL (jumper J2 on the 250466, J3 on the 250469).
8	COLOR	clock	Color clock out: the crystal frequency, buffered (14.31818 MHz NTSC, 17.734472 MHz PAL).
9	VSS	ground	0 V.
10	NC	nc	No connection.
11	NC	nc	No connection.
12	VDD	power	+5 V supply.
13	XTL OUT	clock	Crystal output. The trimmer capacitor to ground on this pin sets the color frequency.
14	XTL IN	clock	Crystal input.
15	VDD	power	+5 V supply.
16	NC	nc	No connection.

Fitted in

Commodore 64 U31 (250425, 250466); U20 on the 250469
Commodore 128 U28

8701 / 7701 clock generator pinout

Pins

Fitted in

Sources