RabbitCore RCM3305, User Manual

Page: 35 / 160

User’s Manual 29
4.1.1 Memory I/O Interface
The Rabbit 3000 address lines (A0–A18) 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 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–PB5 and PB7 can also be used as an external
address bus.
When using the external I/O bus for a digital output 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 external 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 4.2.3.
/RES is an output from the reset circuitry that can be used to reset external peripheral
devices.
4.1.3 LEDs
The RCM3305/RCM3315 has three Ethernet status LEDs located beside the RJ-45 Ether-
net jack—these are discussed in Section 4.2.
Addiitionally, there are two other LEDs. The SF LED at DS3 blinks when data are being
written to or read from the flash mass-storage device. The red USR LED at DS3 is a user-
programmable LED, which is controlled by PD0 on the Rabbit 3000’s Parallel Port D. The
sample program
FLASHLED.C
provided in the Dynamic C
SAMPLES\RCM3300
folder
shows how to set up and use this user-programmable LED.