Reference, Busport | Motorola CMD11E1 instruction

BUS_PORT

The BUS_PORT supports off-board parallel devices. Power (+5V), ground, address lines, data lines, and control lines are brought out to this 34 pin connector. Pin assignments are as follows:

	PIN	BUS_PORT	PIN
GND	1	¨ ¡	2	D3
D2	3	¡ ¡	4	D4
D1	5	¡ ¡	6	D5
D0	7	¡ ¡	8	D6
A0	9	¡ ¡	10	D7
A1	11	¡ ¡	12	A2
A10	13	¡ ¡	14	A3
OE	15	¡ ¡	16	A4
A11	17	¡ ¡	18	A5
A9	19	¡ ¡	20	A6
A8	21	¡ ¡	22	A7
A12	23	¡ ¡	24	A13
W/R	25	¡ ¡	26	CS0
CS1	27	¡ ¡	28	CS2
CS3	29	¡ ¡	30	CS4
CS5	31	¡ ¡	32	IRQ
+5	33	¡ ¡	34	M2

A/D REFERENCE

The VRH and VRL lines from the HC11 are connected to +5v through R3 and to ground through R2 respectively. These two resistors are located next to the MCU_PORT header. The resistors are identified on the silk screen by their reference designators. The appropriate resistor(s) need to be removed in order to apply an external reference to the VRH and/or VRL inputs.