Input/Output (I/O) Ports
Port A
MC68HC908GP32
•
MC68HC08GP32
—
Rev. 6
Technical Data
MOTOROLA
Input/Output (I/O) Ports
217
Figure 16-4. Port A I/O Circuit
When bit DDRAx is a logic 1, reading address $0000 reads the PTAx
data latch. When bit DDRAx is a logic 0, reading address $0000 reads
the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit.
Table 16-2
summarizes
the operation of the port A pins.
READ DDRA ($0004)
WRITE DDRA ($0004)
RESET
WRITE PTA ($0000)
READ PTA ($0000)
PTAx
DDRAx
PTAx
IN
TE
RNA
L D
A
T
A
B
U
S
V
DD
PTAPUEx
INTERNAL
PULLUP
DEVICE
Table 16-2. Port A Pin Functions
PTAPUE Bit
DDRA Bit
PTA Bit
I/O Pin Mode
Accesses
to DDRA
Accesses to PTA
Read/Write
Read
Write
1
0
X
(1)
Input, V
DD
(4)
DDRA7–DDRA0
Pin
PTA7–PTA0
(3)
0
0
X
Input, Hi-Z
(2)
DDRA7–DDRA0
Pin
PTA7–PTA0
(3)
X
1
X
Output
DDRA7–DDRA0
PTA7–PTA0
PTA7–PTA0
NOTES:
1. X = Don’t care
2. Hi-Z = High impedance
3. Writing affects data register, but does not affect input.
4. I/O pin pulled up to V
DD
by internal pullup device
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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