Memory I/O Interface; Other Inputs And Outputs - Rabbit RabbitCore RCM3400 User Manual

4.1.1 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 PB2–PB7 can also be used as an auxiliary address bus.
When using the auxiliary I/O bus for either Ethernet or the LCD/keypad module on the
Prototyping Board or for any other reason, you must add the following line at the begin-
ning of your program.
#define PORTA_AUX_IO // required to enable auxiliary I/O bus

4.1.2 Other Inputs and Outputs

The status, /RESET_IN, SMODE0, and SMODE1 I/O are normally associated with the
programming port. Since the status pin is not used by the system once a program has been
downloaded and is running, the status pin can then be used as a general-purpose CMOS
output. The programming port is described in more detail in Section 4.2.2.
/RESET_IN is an external input used to reset the Rabbit 3000 microprocessor and the
RCM3400 memory. /RES is an output from the reset circuitry that can be used to reset
other peripheral devices.
The two SMODE pins, SMODE0 and SMODE1, are available as inputs. The logic state of
these two pins determines the startup procedure after a reset.
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