MC68HC05K1 FREESCALE [Freescale Semiconductor, Inc], MC68HC05K1 Datasheet - Page 68

• Manufacturer Part Number: MC68HC05K1
• Description: HCMOS Microcontroller Unit
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Technical Data
7.3.3 Pulldown Register A
Technical Data
NOTE:
Address:
Port A pins have mask-optional pulldown devices that sink
approximately 100 A. Clearing the PDIA7–PDIA0 bits in pulldown
register A turns on the port A pulldown devices. Pulldown register A,
shown in
port A pin is an input.
If the pulldown mask option is selected, reset initializes all port A and port
B pins as inputs with pulldown devices turned on.
PDIA7–PDIA0 — Port A Pulldown Inhibit Bits 7–0
To avoid excessive current draw, connect all unused input pins to V
or V
initialization code. Avoid a floating port A input by clearing its pulldown
register bit before changing its DDRA bit from logic 1 to logic 0.
Because pulldown register A is a write-only register, using the
read-modify-write instruction may result in inadvertently turning bits on
or off.
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.
SS
For More Information On This Product,
1 = Corresponding port A pin pulldown device turned off
0 = Corresponding port A pin pulldown device turned on
. Or change I/O pins to outputs by writing to DDRA in user
PDIA7
$0010
Bit 7
Figure
0
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Parallel Input/Output (I/O)
Figure 7-3. Pulldown Register A (PDRA)
= Unimplemented
PDIA6
7-3, can turn on a port A pulldown device only when the
6
0
PDIA5
5
0
PDIA4
4
0
MC68HC05K0 • MC68HC05K1 — Rev. 2.0
PDIA3
3
0
PDIA2
2
0
PDIA1
1
0
PDIA0
Bit 0
0
DD