User’s Manual
29
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.
40–47
LN[0:7]
Analog Input
A/D converter
(RCM4000 only)
48
CONVERT
Analog Input
49
VREF
Analog reference
voltage
1.15 V/2.048 V/2.500 V
on-chip ref. voltage
(RCM4000 only)
50
GND
Ground
Analog ground
Table 2. RCM4000 Pinout Configurations (continued)
Pin
Pin Name
Default Use
Alternate Use
Notes
Summary of Contents for RabbitCore RCM4000
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