MC68HC08AS32 Datasheet, PDF (186/394 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

Input/Output (I/O) Ports
15.3.2 Data Direction Register A
Data direction register A determines 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 corresponding port A pin; a logic 0 disables the output buffer.
Address: $0004
Bit 7
6
5
4
3
2
1
Read:
DDRA7 DDRA6 DDRA5 DDRA4 DDRA3 DDRA2 DDRA1
Write:
Reset:
Unaffected by Reset
Figure 15-2. Data Direction Register A (DDRA)
Bit 0
DDRA0
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 15-3 shows the port A I/O logic.
READ DDRA ($0004)
WRITE DDRA ($0004)
RESET
DDRAx
WRITE PTA ($0000)
PTAx
PTAx
READ PTA ($0000)
Figure 15-3. Port A I/O Circuit
Advance Information
186
Input/Output (I/O) Ports
MC68HC08AS32 — Rev. 3.0
MOTOROLA