Jameco Electronics Rabbit 3000 - Manual (Page 139)

130 Rabbit 3000 Microprocessor
9.1 Parallel Port A
Parallel Port A has a single read/write register:
This register should not be used if the slave port or auxiliary I/O bus is enabled.
The slave port control register is used to control whether Parallel Port A is configured as
slave databus, auxiliary I/O data bus, parallel Input or parallel output. To make the port an
input, store 0x080 in the SPCR (slave port control register). To make the port an output,
store 0x084 in SPCR. Parallel Port A is set up as an input port on reset.
When the port is read, the value read reflects the voltages on the pins, "1" for high and "0"
for low. This could be different than the value stored in the output register if the pin is
forced to a different state by an external voltage.
NOTE: Refer to Section 9.6.1, “Using Parallel Port A and Parallel Port F,” for more
information.
Table 9-1. Parallel Port A Registers
Register Name Mnemonic I/O address R/W Reset
Port A Data Register PADR 0x30 R/W xxxxxxxx
Slave Port Control Register SPCR 0x24 R/W 0xx00000
Table 9-2. Parallel Port A Data Register Bit Functions
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
PADR (R/W)
adr = 0x030
PA7 PA6 PA5 PA4 PA3 PA2 PA1 PA0