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4.1.1 Memory I/O Interface
The Rabbit 4000 address lines (A0–A19) and all the data lines (D0–D7) are routed internally to
the onboard flash memory and SRAM chips. I/0 write (/IOWR) and I/0 read (/IORD) are avail-
able for interfacing to external devices, and are also used by the RCM4510W.
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 external 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 external 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
J1 instead of the PE5–PE7 pins 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 RCM4510W memory. /RESET_OUT is an
output from the reset circuitry that can be used to reset other peripheral devices.
4.1.3 Auxiliary I/O
Up to nine additional digital I/O, up to four of which may be configured in software as analog
inputs, a +3.3 V DC power supply point and ground, and a SYS_PWR_ON line are brought out
on auxiliary I/O header J4. Section 4.4 describes the use of these lines in more detail.
User's Manual
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