mc68hc908sr12 Freescale Semiconductor, Inc, mc68hc908sr12 Datasheet - Page 326

• Manufacturer Part Number: mc68hc908sr12
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Input/Output (I/O) Ports
Data Sheet
326
NOTE:
DDRB[6:0] — Data Direction Register B Bits
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.
the port B I/O logic.
When DDRBx is a logic 1, reading address $0001 reads the PTBx data
latch. When 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 18-4
Notes:
1. X = don’t care.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect input.
DDRB
These read/write bits control port B data direction. Reset clears
DDRB[6:0], configuring all port B pins as inputs.
Bit
0
1
1 = Corresponding port B pin configured as output
0 = Corresponding port B pin configured as input
READ DDRB ($0005)
WRITE DDRB ($0005)
WRITE PTB ($0001)
READ PTB ($0001)
PTB Bit
X
summarizes the operation of the port B pins.
X
(1)
Input/Output (I/O) Ports
Table 18-4. Port B Pin Functions
Input, Hi-Z
I/O Pin Mode
RESET
Figure 18-8. Port B I/O Circuit
Output
(2)
MC68HC908SR12•MC68HC08SR12 — Rev. 5.0
Accesses to DDRB
DDRBx
PTBx
DDRB[6:0]
DDRB[6:0]
Read/Write
# PTB3–PTB0 are open-drain pins when configured as outputs.
Freescale Semiconductor
PTB[6:0]
Figure 18-8
Read
Pin
Accesses to PTB
PTB[6:0]
PTB[6:0]
shows
Write
PTBx
(3)
#