cOMMODORE 1571 sERVICE mANUAL: ic pIN aSSIGNMENTS

40/42 pin gate array

40 pin	42 pin	desc	function
1	1	test	iNPUT USED IN DESIGN VERIFICATION.
2-9	2-9	yb0-yb7	dATA INPUT/OUTPUT LINES FOR READ/WRITE OPERATION.
10	10	vSS	gROUND.
11,12	11,12	stp0,stp1	iNPUT TO STEPPER DRIVER.
13	13	mtr	cONTROL LINE USED TO ACTIVATE THE STEPPER MOTOR.
14	14	a	wRITE PROTECT INPUT. iNDICATES DISK IS WRITE PROTECTED.
15,16	15,16	ds0,ds1	iNPUTS USED TO PRODUCE THE BINARY COUNT FOR THE FREQUENCY DIVIDE RATIO.
17	17	sync	sYNC OUTPUT.
18	18	ted	a LOW INPUT CLEARS THE byte LINE IN 2 mhZ MODE. a HIGH SETS 1541 MODE.
19	19	oe	iNPUT TO READ/WRITE BLOCK TO SET MODE. 0 FOR wRITE, 1 FOR rEAD.
20	20	accl	iNPUT SELECT LINE FOR THE cpu CLOCK. 0 FOR 1541 - 1 mhZ, 1 FOR 1571 - 2 mhZ.
xx	21,22		n/c
21	23	osc	16 mhZ CLOCK INPUT.
22	24	atna	aTTENTION ACKNOWLEDGE INPUT.
23	25	atni	aTTENTION LINE INPUT FROM SERIAL BUS.
24	26	atn	aTTENTION DATA INPUT FROM SERIAL BUS.
25-28	27-30	y0-y3	cONTROL OUTPUT LINES FOR THE 4 PHASES OF THE STEPPER MOTOR.
29	31	xrw	ram WRITE ENABLE OUTPUT.
30	32	vCC	+5vdc.
31	33	clr	hIGH INPUT WHEN THE READ DATA IS LOGICAL 1.
32	34	pll	iNPUT FROM THE 20 PIN GATE ARRAY. cLOCK COMPENSATION.
33	35	lock	iNDICATES THE pll lock STATUS. wHEN LOGICAL 1, pll IS LOCKED. wHEN 0, THE INTERNAL CLOCK IS USED FOR SAMPLING DATA.
34	36	r/w	r/w SELECT INPUT.
35,36	37,38	q,qX	wRITE PULSE OUTPUTS.
37	39	ck	cLOCK SELECT OUTPUT - 1 OR 2 mhZ.
38	40	b	wRITE ENABLE OUTPUT.
39	41	soe	eNABLE BYTE INPUT.
40	42	byte	dATA LATCHED OUTPUT.