Digi Rabbit 5000, User Manual

Page: 127 / 414

Chapter 12 Parallel Port E 127
12.2.3 Other Registers
12.2.4 Interrupts
External interrupts can be accepted from pins PE5, PE4, PE1 or PE0; see Chapter 7 for
more details.
12.3 Operation
The following steps must be taken before using Parallel Port E.
1. Select the desired input/output direction for each pin via PEDDR.
2. Select high/low or open-drain functionality for outputs via PEDCR.
3. If an alternative peripheral output function is desired for a pin, select it via PEALR or
PEAHR and then enable it via PEFR. Refer to the appropriate peripheral chapter for
further use of that pin.
Once the port is set up, data can be read or written by accessing PEDR. Read PEDR to
learn the current state of a Parallel Port E pin; any value written to an input pin will not
appear on that pin until that pin becomes an output.
Register Function
SACR, SBCR, SCCR,
SDCR, SECR, SFCR Select a Parallel Port E pin as serial data (and
optional clock) input.
ICS1R, ICS2R
Select a Parallel Port E pin as a start/stop condition
for Input Capture input.
QDCR
Select a Parallel Port E pin as a Quadrature Decoder
input.
I0CR, I1CR
Select a Parallel Port E pin as an external interrupt
input.
DMR0CR, DMR1CR
Select a Parallel Port E pin as an external DMA
request input.
SPCR Select slave chip select on PE7.
IHCR, IHSR, IHTR Select a Parallel Port E pin for I/O handshake.