Rabbit Rabbit 4000, User Manual

Page: 101 / 358

Chapter 11 Parallel Port D 91
11.2.3 Other Registers
11.2.4 Interrupts
External interrupts can be accepted from pins PD1 or PD0; see Chapter 7 for more details.
11.3 Operation
The following steps must be taken before using Parallel Port D.
1. Select the desired input/output direction for each pin via PDDDR.
2. Select high/low or open-drain functionality for outputs via PDDCR.
3. If an alternative peripheral output function is desired for a pin, select it by via PDALR
or PDAHR and then enable it via PDFR. Refer to the appropriate peripheral chapter for
further use of that pin.
4. All these settings will be superseded if a 16-bit memory interface is selected since par-
allel port D is used for the upper half of the data bus in that mode.
Once Parallel Port D is set up, data can be read or written by accessing PDDR. The value
of an output pin read in from PDDR will reflect its current output value, but any value
written to an input pin will not appear until that pin becomes an output.
Register Function
SACR, SBCR, SCCR,
SDCR, SECR, SFCR Select a Parallel Port D pin as serial data (and
optional clock) input.
ICS1R, ICS2R
Select a Parallel Port D pin as a start/stop condition
input.
QDCR Select a Parallel Port D pin as a decoder input.
I0CR, I1CR
Select a Parallel Port D pin as an external interrupt
input.
DMR0CR, DMR1CR
Select a Parallel Port D pin as an external DMA
request input.
MACR Enable 16-bit data bus.