MC68HC08AS32 Datasheet, PDF (189/394 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

Input/Output (I/O) Ports
Port B
15.4.2 Data Direction Register B
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
6
5
4
3
2
1
Read:
DDRB7 DDRB6 DDRB5 DDRB4 DDRB3 DDRB2 DDRB1
Write:
Reset: 0
0
0
0
0
0
0
Figure 15-5. 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 15-6 shows the port B I/O logic.
READ DDRB ($0005)
WRITE DDRB ($0005)
RESET
WRITE PTB ($0001)
READ PTB ($0001)
DDRBx
PTBx
PTBx
Figure 15-6. Port B I/O Circuit
MC68HC08AS32 — Rev. 3.0
MOTOROLA
Input/Output (I/O) Ports
Advance Information
189