MC908JL3ECPE Datasheet, PDF (109/180 Pages) Freescale Semiconductor, Inc – Microcontrollers

READ DDRB ($0005)
WRITE DDRB ($0005)
RESET
WRITE PTB ($0001)
DDRBx
PTBx
Port B
PTBx
READ PTB ($0001)
To Analog-To-Digital Converter
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
0
X⁽¹⁾
Input, Hi-Z⁽²⁾
1
X
Output
Accesses to DDRB
Read/Write
DDRB[7:0]
DDRB[7:0]
Accesses to PTB
Read
Pin
Write
PTB[7:0]⁽³⁾
Pin
PTB[7:0]
1. X = don’t care.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect the input.
MC68HC908JL3E Family Data Sheet, Rev. 4
Freescale Semiconductor
109