MC908JB16DWE Datasheet, PDF (267/332 Pages) Freescale Semiconductor, Inc – Microcontrollers

Input/Output (I/O) Ports
14.3.2 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
Write:
DDRA6
DDRA5
DDRA4
DDRA3
DDRA2
DDRA1
Reset: 0*
0
0
0
0
0
0
* DDRA7 bit is reset by POR or LVI reset only.
Figure 14-3. Data Direction Register A (DDRA)
Bit 0
DDRA0
0
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 14-4 shows the port A I/O logic.
READ DDRA ($0004)
WRITE DDRA ($0004)
RESET
WRITE PTA ($0000)
DDRAx
PTAx
PTAx
READ PTA ($0000)
MC68HC908JB16 — Rev. 1.1
Freescale Semiconductor
Figure 14-4. Port A I/O Circuit
Input/Output (I/O) Ports
Technical Data
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