Operation - Rabbit 6000 User Manual

9.3 Operation

The following steps must be taken before using Parallel Port B.
1. Select the desired input/output direction for each pin via PBDDR. Note that this setting is super-
seded for some pins if the slave port or external I/O bus is enabled in SPCR or if the clocked serial
mode is enabled for Serial Ports A or B.
2. If a particular drive strength, slew rate, or pullup/down resistor status is desired for a Parallel Port B
pin, set that in the appropriate PBxCR.
3. If the slave port or the external I/O bus is selected, refer to the chapters for those peripherals for fur-
ther setup information.
Once the port is set up, data can be read or written by accessing PBDR. The value in PBDR of an output
pin will reflect its current output value, but any value written to an input pin will not appear on that pin
until that pin becomes an output.
If one of the Flexible Interface Module has been enabled to use Parallel Port B, writing to PBDR will no
longer change the state of the pins. The other Parallel Port B registers are still valid. Refer to Chapter 33
for more details.
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