mc68hc705k1 Freescale Semiconductor, Inc, mc68hc705k1 Datasheet - Page 66

• Manufacturer Part Number: mc68hc705k1
• Description: Hcmos Microcontroller Unit
• Manufacturer: Freescale Semiconductor, Inc

Parallel Input/Output (I/O)
7.4.3 Pulldown Register A
Technical Data
NOTE:
Address:
Programming the SWPDI bit in the mask option register to a logic 0
enables the port A and port B pulldown devices. The port A pulldown
devices sink approximately 100 A and are under the control of the
PDIA7–PDIA0 bits in pulldown register A (PDRA).
Clearing the PDIA7–PDIA0 bits turns on the pulldown devices of the port
A pins that are configured as inputs. A pulldown device can be turned on
only when its pin is an input. When SWPDI is a logic 0, reset initializes
all port A pins as inputs with pulldown devices turned on.
Programming the SWPDI bit to a logic 1 disables the port A and port B
pulldown devices. Reset initializes all port A pins as inputs with pulldown
devices disabled when the SWPDI bit is programmed to a logic 1.
PDIA7–PDIA0 — Port A Pulldown Inhibit Bits 7–0
Avoid a floating port A input by clearing its pulldown register bit before
changing its DDRA bit from logic 1 to logic 0.
Do not use read-modify-write instructions on pulldown register A.
Reset:
Read:
Write:
Writing logic 0s to these write-only bits turns on the port A pulldown
devices. Reading pulldown register A returns undefined data. Reset
clears bits PDIA7–PDIA0.
Freescale Semiconductor, Inc.
For More Information On This Product,
1 = Corresponding port A pin pulldown device turned off
0 = Corresponding port A pin pulldown device turned on
PDIA7
$0010
Bit 7
0
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Parallel Input/Output (I/O)
Figure 7-3. Pulldown Register A (PDRA)
= Unimplemented
PDIA6
6
0
PDIA5
5
0
PDIA4
4
0
PDIA3
3
0
MC68HC705K1 — Rev. 2.0
PDIA2
2
0
PDIA1
1
0
PDIA0
Bit 0
0