Freescale Semiconductor, Inc.
Input/Output (I/O) Ports
Port A
READ DDRA ($0004)
WRITE DDRA ($0004)
V
DD
KBIEX
INTERNAL
PULLUP
DEVICE
DDRAx
RESET
WRITE PTA ($0000)
PTAx
PTAx
READ PTA ($0000)
Figure 13-4. Port A I/O Circuit
Table 13-1. Port A Pin Functions
Accesses
to DDRA
Accesses to PTA
(2)
KBIE
Bit
DDRA Bit
PTA Bit
I/O Pin Mode
Read/Write
Read
Write
PTA[7:0]
PTA[7:0]
(4)
(1)
(3)
(3)
1
X
DDRA[7:0]
Pin
Input, V
X
DD
(5)
0
0
0
1
X
X
DDRA[7:0]
DDRA[7:0]
Pin
Input, Hi-Z
Output
PTA[7:0]
PTA[7:0]
Notes:
1. X = Don’t care
2. Keyboard interrupt enable bit (see 14.6.2 Keyboard Interrupt Enable Register)
3. Writing affects data register, but does not affect input.
4. I/O pin pulled up to V by internal pullup device
DD
5. Hi-Z = High impedance
NOTE: Setting a keyboard interrupt enable bit (KBIEx) forces the corresponding
keyboard interrupt pin to be an input, overriding the data direction
register. However, the data direction register bit must be a logic 0 for
software to read the pin.
MC68HC908RFRK2
MOTOROLA
AdvanceInformation
179
Input/Output (I/O) Ports
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