MC68HC08AS20 Datasheet, PDF (185/386 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

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, or logic 0 if that particular bit is in use by the
ADC. The data latch can always be written, regardless of the state of its
data direction bit. Table 15-3 summarizes the operation of the port B
pins.
Table 15-3. Port B Pin Functions
DDRB PTB Bit in Use
Bit Bit by ADC
I/O Pin
Mode
Accesses
to DDRB
Read/Write
0
X
No
Input, Hi-Z DDRB[7:0]
1
X
No
Output DDRB[7:0]
0
X
Yes
Input, Hi-Z DDRB[7:0]
1
X
Yes
Input, Hi-Z DDRB[7:0]
X = don’t care
Hi-Z = high impedance
1. Writing affects data register, but does not affect input.
Accesses to PTB
Read
Pin
Write
PTB[7:0]⁽¹⁾
PTB[7:0] PTB[7:0]
0
PTB[7:0]⁽¹⁾
PTB[7:0] PTB[7:0]
MC68HC08AS20 — Rev. 4.1
Freescale Semiconductor
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