Z-World RabbitCore RCM3200 User Manual - page 15

User’s Manual

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2.1.1  Memory I/O Interface

The Rabbit 3000 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 PB3–PB7 can also be used as an external address bus.

When using  the auxiliary I/O bus, you must add the following line at the beginning of 

your program.

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

The STATUS output has three different programmable functions:

1. It can be driven low on the first op code fetch cycle.

2. It can be driven low during an interrupt acknowledge cycle.

3. It can also serve as a general-purpose output.

2.1.2  Other Inputs and Outputs

Two status mode pins, SMODE0 and SMODE1, are available as inputs. The logic state of 

these two pins determines the startup procedure after a reset.

/RESET_IN is an external input used to reset the Rabbit 3000 microprocessor and the 

RCM3200 memory. /RES is an output from the reset circuitry that can be used to reset 

other peripheral devices.