MC68HC908GZ8 Datasheet, PDF (206/344 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Input/Output (I/O) Ports
READ DDRB ($0005)
WRITE DDRB ($0005)
RESET
WRITE PTB ($0001)
DDRBx
PTBx
PTBx
READ PTB ($0001)
Figure 17-8. Port B I/O Circuit
When bit DDRBx is a logic 1, reading address $0001 reads the PTBx data latch.
When bit DDRBx is a logic 0, reading address $0001 reads the voltage level on the
pin. The data latch can always be written, regardless of the state of its data
direction bit. Table 17-3 summarizes the operation of the port B pins.
Table 17-3. Port B Pin Functions
DDRB PTB
Bit
Bit
I/O Pin
Mode
Accesses
to DDRB
Read/Write
0
X⁽¹⁾
Input, Hi-Z⁽²⁾
DDRB7–DDRB0
1
X
Output
DDRB7–DDRB0
1. X = Don’t care
2. Hi-Z = High impedance
3. Writing affects data register, but does not affect input.
Accesses
to PTB
Read
Write
Pin
PTB7–PTB0⁽³⁾
PTB7–PTB0
PTB7–PTB0
Data Sheet
206
Input/Output (I/O) Ports
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MC68HC908GZ8
MOTOROLA