MC68HC908AB32 Datasheet, PDF (319/392 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Input/Output (I/O) Ports
17.4.2 Data Direction Register B (DDRB)
Data direction register B determines whether each port B pin is an input
or an output. Writing a logic 1 to a DDRB bit enables the output buffer for
the corresponding port B pin; a logic 0 disables the output buffer.
Address: $0005
Bit 7
Read:
DDRB7
Write:
Reset: 0
6
DDRB6
0
5
DDRB5
0
4
DDRB4
0
3
DDRB3
0
2
DDRB2
0
1
DDRB1
0
Figure 17-6. Data Direction Register B (DDRB)
Bit 0
DDRB0
0
DDRB[7:0] — Data Direction Register B Bits
These read/write bits control port B data direction. Reset clears
DDRB[7:0], configuring all port B pins as inputs.
1 = Corresponding port B pin configured as output
0 = Corresponding port B pin configured as input
NOTE:
Avoid glitches on port B pins by writing to the port B data register before
changing data direction register B bits from 0 to 1. Figure 17-7 shows
the port B I/O logic.
READ DDRB ($0005)
WRITE DDRB ($0005)
RESET
WRITE PTB ($0001)
DDRBx
PTBx
PTBx
READ PTB ($0001)
To Analog-To-Digital Converter
Figure 17-7. Port B I/O Circuit
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Input/Output (I/O) Ports
Technical Data
319