MC68HC908QC16_07 Datasheet, PDF (115/274 Pages) Freescale Semiconductor, Inc – Microcontrollers

Port D
PTD[7:0] — Port D Data Bits
These read/write bits are software programmable. Data direction of each port D pin is under the control
of the corresponding bit in data direction register D. Reset has no effect on port D data.
11.6.2 Data Direction Register D
Data direction register D (DDRD) determines whether each port D pin is an input or an output. Writing a
1 to a DDRD bit enables the output buffer for the corresponding port D pin; a 0 disables the output buffer.
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
DDRD7 DDRD6 DDRD5 DDRD4 DDRD3 DDRD2 DDRD1
0
0
0
0
0
0
0
Figure 11-14. Data Direction Register D (DDRD)
Bit 0
DDRD0
0
DDRD[7:0] — Data Direction Register D Bits
These read/write bits control port D data direction. Reset clears DDRD[7:0], configuring all port D pins
as inputs.
1 = Corresponding port D pin configured as output
0 = Corresponding port D pin configured as input
NOTE
Avoid glitches on port D pins by writing to the port D data register before
changing data direction register D bits from 0 to 1. Figure 11-15 shows the
port D I/O logic.
READ DDRD ($0007)
WRITE DDRD ($0007)
RESET
WRITE PTD ($0003)
DDRDx
PTDx
PTDPUEx
PULLUP
PTDx
READ PTD ($0003)
Figure 11-15. Port D I/O Circuit
When DDRDx is a 1, reading address $0003 reads the PTDx data latch. When DDRDx is a 0, reading
address $0003 reads the voltage level on the pin. The data latch can always be written, regardless of the
state of its data direction bit.
MC68HC908QC16 • MC68HC908QC8 • MC68HC908QC4 Data Sheet, Rev. 3
Freescale Semiconductor
115