mc68hc908bd48 Freescale Semiconductor, Inc, mc68hc908bd48 Datasheet - Page 234

• Manufacturer Part Number: mc68hc908bd48
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Input/Output (I/O) Ports
17.3.2 Data Direction Register A
Data Sheet
234
NOTE:
Address:
Data direction register A (DDRA) 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.
DDRA7–DDRA0 — Data Direction Register A Bits
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 17-3
Reset:
Read:
Write:
These read/write bits control port A data direction. Reset clears
DDRA7–DDRA0, configuring all port A pins as inputs.
1 = Corresponding port A pin configured as output
0 = Corresponding port A pin configured as input
DDRA7
READ DDRA ($0004)
WRITE DDRA ($0004)
WRITE PTA ($0000)
READ PTA ($0000)
$0004
Bit 7
0
Figure 17-2. Data Direction Register A (DDRA)
shows the port A I/O logic.
Input/Output (I/O) Ports
DDRA6
6
0
Figure 17-3. Port A I/O Circuit
RESET
DDRA5
5
0
DDRA4
DDRAx
PTAx
4
0
DDRA3
3
0
MC68HC908BD48
DDRA2
Freescale Semiconductor
2
0
DDRA1
1
0
—
Rev. 2.1
DDRA0
Bit 0
PTAx
0