Datasheet

Port B
MC68HC908JL3E Family Data Sheet, Rev. 4
Freescale Semiconductor 109
Figure 10-8. Port B I/O Circuit
When DDRBx is a 1, reading address $0001 reads the PTBx data latch. When DDRBx is a 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 10-3 summarizes the operation of the port B pins.
Table 10-3. Port B Pin Functions
DDRB Bit PTB Bit I/O Pin Mode
Accesses to DDRB Accesses to PTB
Read/Write Read Write
0X
(1)
1. X = don’t care.
Input, Hi-Z
(2)
2. Hi-Z = high impedance.
DDRB[7:0] Pin PTB[7:0]
(3)
3. Writing affects data register, but does not affect the input.
1 X Output DDRB[7:0] Pin PTB[7:0]
READ DDRB ($0005)
WRITE DDRB ($0005)
RESET
WRITE PTB ($0001)
READ PTB ($0001)
PTBx
DDRBx
PTBx
INTERNAL DATA BUS
To Analog-To-Digital Converter