s908gz60cfa Freescale Semiconductor, Inc, s908gz60cfa Datasheet - Page 177

• Manufacturer Part Number: s908gz60cfa
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

DDRB7–DDRB0 — Data Direction Register B Bits
Figure 13-8
When bit DDRBx is a 1, reading address $0001 reads the PTBx data latch. When bit 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.
Freescale Semiconductor
1. X = Don’t care
2. Hi-Z = High impedance
3. Writing affects data register, but does not affect input.
These read/write bits control port B data direction. Reset clears DDRB7–DDRB0, configuring all port
B pins as inputs.
DDRB
Bit
0
1
1 = Corresponding port B pin configured as output
0 = Corresponding port B pin configured as input
shows the port B I/O logic.
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.
PTB
X
Bit
X
(1)
MC68HC908GZ60 • MC68HC908GZ48 • MC68HC908GZ32 Data Sheet, Rev. 6
READ DDRB ($0005)
WRITE DDRB ($0005)
WRITE PTB ($0001)
READ PTB ($0001)
Input, Hi-Z
I/O Pin
Output
Mode
Table 13-3. Port B Pin Functions
(2)
RESET
Figure 13-8. Port B I/O Circuit
Table 13-3
Accesses to DDRB
NOTE
DDRB7–DDRB0
DDRB7–DDRB0
DDRBx
PTBx
Read/Write
summarizes the operation of the port B pins.
PTB7–PTB0
Read
Pin
Accesses to PTB
PTBx
PTB7–PTB0
PTB7–PTB0
Write
Port B
(3)
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