MC68HC908AZ60 Datasheet, PDF (310/480 Pages) Motorola, Inc – HCMOS Microcontroller Unit

I/O Ports
DDRA[7:0] — Data Direction Register A Bits
These read/write bits control port A data direction. Reset clears
DDRA[7:0], configuring all port A pins as inputs.
1 = Corresponding port A pin configured as output
0 = Corresponding port A pin configured as input
NOTE: Avoid glitches on port A pins by writing to the port A data register before
changing data direction register A bits from 0 to 1.
Figure 4 shows the port A I/O logic.
READ DDRA ($0004)
WRITE DDRA ($0004)
RESET
WRITE PTA ($0000)
READ PTA ($0000)
DDRAx
PTAx
PTAx
Figure 4. Port A I/O Circuit
When bit DDRAx is a logic 1, reading address $0000 reads the PTAx
data latch. When bit DDRAx is a logic 0, reading address $0000 reads
the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 1 summarizes the
operation of the port A pins.
MC68HC908AZ60 — Rev 2.0
308
I/O Ports
4-io
MOTOROLA