mc68hc908lb8 Freescale Semiconductor, Inc, mc68hc908lb8 Datasheet - Page 135

• Manufacturer Part Number: mc68hc908lb8
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

DDRA6–DDRA0 — Data Direction Register A Bits
Figure 14-4
When bit DDRAx is a 1, reading address $0000 reads the PTAx data latch. When bit DDRAx is a 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.
Freescale Semiconductor
PTAPUE
These read/write bits control port A data direction. Reset clears DDRA6–DDRA0, configuring all port
A pins as inputs.
Bit
1 = Corresponding port A pin configured as output
0 = Corresponding port A pin configured as input
X
1
0
shows the port A I/O logic.
Address:
Avoid glitches on port A pins by writing to the port A data register before
changing data direction register A bits from 0 to 1.
DDRA
Reset:
Read:
Write:
Bit
0
0
1
PTAPUEx
READ DDRA ($0004)
WRITE DDRA ($0004)
WRITE PTA ($0000)
READ PTA ($0000)
$0004
Bit 7
0
0
PTA
X
Bit
X
X
(1)
Figure 14-3. Data Direction Register A (DDRA)
DDRA6
6
0
Input, Hi-Z
Input, V
Table 14-1. Port A Pin Functions
RESET
Figure 14-4. Port A I/O Circuit
I/O Pin
Output
MC68HC908LB8 Data Sheet, Rev. 1
Mode
V
DD
INTERNAL
PULLUP
DEVICE
DDRA5
DD
5
0
(2)
(4)
Table 14-1
NOTE
DDRA4
DDRAx
PTAx
4
0
DDRA6–DDRA0
DDRA6–DDRA0
DDRA6–DDRA0
Read/Write
Accesses
to DDRA
summarizes the operation of the port A pins.
DDRA3
3
0
DDRA2
2
0
PTA6–PTA0
Read
Pin
Pin
DDRA1
1
0
Accesses
to PTA
DDRA0
Bit 0
PTAx
0
PTA6–PTA0
PTA6–PTA0
PTA6–PTA0
Write
Port A
(3)
(3)
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