MC68HC705C8A Datasheet, PDF (77/222 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Parallel Input/Output (I/O)
Port A
7.3.2 Data Direction Register A
The contents of data direction register A (DDRA) shown in Figure 7-2
determine whether each port A pin is an input or an output. Writing a
logic 1 to a DDRA bit enables the output buffer for the associated port A
pin; a logic 0 disables the output buffer. A reset clears all DDRA bits,
configuring all port A pins as inputs.
Address: $0004
Bit 7
6
5
4
3
2
1
Read:
DDRA7 DDRA6 DDRA5 DDRA4 DDRA3 DDRA2 DDRA1
Write:
Reset: 0
0
0
0
0
0
0
Figure 7-2. Data Direction Register A (DDRA)
Bit 0
DDRA0
0
DDRA7–DDRA0 — Port A Data Direction Bits
These read/write bits control port A data direction. Reset clears bits
DDRA7–DDRA0.
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 DDRA bits from logic 0 to logic 1.
MC68HC705C8A — Rev. 2.0
MOTOROLA
Parallel Input/Output (I/O)
Technical Data
77