Digi RCM4000 user manual Memory I/O Interface, Other Inputs and Outputs

Table 2. RCM4000 Pinout Configurations (continued)

Pin	Pin Name	Default Use	Alternate Use	Notes
40–47	LN[0:7]	Analog Input		A/D converter
				(RCM4000 only)
48	CONVERT	Analog Input
		Analog reference		1.15 V/2.048 V/2.500 V
49	VREF			on-chip ref. voltage
		voltage
				(RCM4000 only)
50	GND	Ground		Analog ground

4.1.1 Memory I/O Interface

The Rabbit 4000 address lines (A0–A19) and all the data lines (D0–D7) are routed inter- nally to the onboard flash memory and SRAM chips. I/0 write (/IOWR) and I/0 read (/IORD) are available for interfacing to external devices.

Parallel Port A can also be used as an external I/O data bus to isolate external I/O from the main data bus. Parallel Port B pins PB2–PB7 can also be used as an auxiliary address bus.

When using the auxiliary I/O bus for any reason, you must add the following line at the beginning of your program.

#define PORTA_AUX_IO // required to enable auxiliary I/O bus

Selected pins on Parallel Ports D and E as specified in Table 2 may be used for input capture, quadrature decoder, DMA, and pulse-width modulator purposes.

4.1.2 Other Inputs and Outputs

The status and the two SMODE pins, SMODE0 and SMODE1, can be brought out to header J3 instead of PE5–PE7 as explained in Appendix A.6.

/RESET_IN is normally associated with the programming port, but may be used as an external input to reset the Rabbit 4000 microprocessor and the RCM4000 memory. /RESET_OUT is an output from the reset circuitry that can be used to reset other peripheral devices.

User’s Manual 29