mc68hc908gr8a Freescale Semiconductor, Inc, mc68hc908gr8a Datasheet - Page 121

• Manufacturer Part Number: mc68hc908gr8a
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

DDRB5–DDRB0 — Data Direction Register B Bits
Figure 12-8
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 DDRB5–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.
PTB
X
Bit
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.
For those devices packaged in a 28-pin DIP and SOIC package, PTB5,4
are not connected. Set DDRB5,4 to a 1 to configure PTB5,4 as outputs.
X
(1)
READ DDRB ($0005)
WRITE DDRB ($0005)
WRITE PTB ($0001)
READ PTB ($0001)
Input, Hi-Z
I/O Pin
MC68HC908GR8A • MC68HC908GR4A Data Sheet, Rev. 5
Output
Mode
(2)
Table 12-3. Port B Pin Functions
RESET
Figure 12-8. Port B I/O Circuit
Accesses to DDRB
DDRB5–DDRB0
DDRB5–DDRB0
Table 12-3
Read/Write
NOTE
DDRBx
PTBx
summarizes the operation of the port B pins.
PTB5–PTB0
Read
Pin
Accesses to PTB
PTBx
PTB5–PTB0
PTB5–PTB0
Write
(3)
Port B
121