
Technical Data
MC68HC705C4A MC68HSC705C4A — Rev. 3.0
Parallel Input/Output (I/O)
Parallel Input/Output (I/O)
7.4.2 Data Direction Register B
The contents of data direction register B (DDRB) shown in Figure 7-5 determine whether each port B pin is an input or an output. Writing a
logic 1 to a DDRB bit enables the output buffer for the associated port B
pin; a logic 0 disables the output buffer. A reset clears all DDRB bits,
configuring all port B pins as inputs. If the pullup devices are enabled by
mask option, setting a DDRB bit to a logic 1 turns off the pullup device
for that pin.
DDRB7–DDRB0 — Port B Data Direction Bits
These read/write bits control port B data direction. Reset clears bits
DDRB7–DDRB0.
1 = Corresponding port B pin configured as output
0 = Corresponding port B pin configured as input
NOTE:
Avoid glitches on port B pins by writing to the port B data register before
changing DDRB bits from logic 0 to logic 1.
Address:
$0005
Bit 7
6
54321
Bit 0
Read:
DDRB7
DDRB6
DDRB5
DDRB4
DDRB3
DDRB2
DDRB1
DDRB0
Write:
Reset:
00
000000
Figure 7-5. Data Direction Register B (DDRB)
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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