Rabbit RabbitCore RCM3400 User Manual page 34

Alternate Uses of the Programming Port
All three clocked Serial Port A signals are available as
• a synchronous serial port
• an asynchronous serial port, with the clock line usable as a general CMOS I/O pin
The programming port may also be used as a serial port via the connector on the
DIAG
programming cable.
In addition to Serial Port A, the Rabbit 3000 startup-mode (SMODE0, SMODE1), status,
and reset pins are available on the programming port.
The two startup mode pins determine what happens after a reset—the Rabbit 3000 is
either cold-booted or the program begins executing at address 0x0000.
The status pin is used by Dynamic C to determine whether a Rabbit microprocessor is
present. 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.
The /RESET_IN pin is an external input that is used to reset the Rabbit 3000 and the
RCM3400 onboard peripheral circuits. The serial programming port can be used to force a
hard reset on the RCM3400 by asserting the /RESET_IN signal.
Refer to the for more information.
Rabbit 3000 Microprocessor User's Manual
28 RabbitCore RCM3400