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Rabbit 3000 Microprocessor User’s Manual
8.2 Dependencies
8.2.1 I/O Pins
Parallel Port A uses pins PA0 through PA7. These pins can be used as follows.
General-purpose 8-bit data input (write 0x080 to SPCR)
General-purpose 8-bit data output (write 0x084 to SPCR)
Slave port data bus (write 0x088 to SPCR)
Data bus of the external I/O bus (write 0x08C to SPCR)
All Parallel Port A bits are inputs at startup or reset.
See the associated peripheral chapters for details on how they use Parallel Port A.
8.2.2 Clocks
Any outputs on Parallel Port A are clocked by the peripheral clock.
8.2.3 Other Registers
8.2.4 Interrupts
There are no interrupts associated with Parallel Port A.
8.3 Operation
The following steps explain how to set up Parallel Port A.
1. Select the desired mode using SPCR.
2. If the slave port or external I/O bus is selected, refer to the chapters for those peripher-
als for further setup.
Once Parallel Port A is set up, data can be read or written by accessing PADR. Note that
Parallel Port A is not available for general-purpose I/O while the slave port or the external
I/O bus is selected. Selecting these options for Parallel Port A affects Parallel Port B
because Parallel Port B is then used for address and control signals.
NOTE: There may be a conflict in using Parallel Port A and Parallel Port F on the original
Rabbit 3000 chip. Either Parallel Port A can be used as inputs, in which case Parallel
Port F has full function, or if Parallel Port A cannot be used as inputs, use any pins on
Parallel Port F not used for PWM or serial clock outputs as inputs and take the precau-
tion of setting up Parallel Port F before the conflicting functionality of Parallel Port A is
enabled. Refer to Rabbit’s Technical Note TN228, Rabbit 3000 Parallel Port F Bug,
for more information.
Register
Function
SPCR
Used to set up Parallel Port A.