MC908AS60ACFU Datasheet, PDF (250/414 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Input/Output Ports
22.2 Port A
Port A is an 8-bit general-purpose bidirectional I/O port.
22.2.1 Port A Data Register
The port A data register contains a data latch for each of the eight port A pins.
Address:
Read:
Write:
Reset:
$0000
Bit 7
PTA7
6
PTA6
5
PTA5
4
3
PTA4
PTA3
Unaffected by Reset
2
PTA2
1
PTA1
Bit 0
PTA0
Figure 22-2. Port A Data Register (PTA)
PTA[7:0] — Port A Data Bits
These read/write bits are software programmable. Data direction of each port A pin is under the control
of the corresponding bit in data direction register A. Reset has no effect on port A data.
22.2.2 Data Direction Register A
Data direction register A determines whether each port A pin is an input or an output. Writing a logic 1 to
a DDRA bit enables the output buffer for the corresponding port A pin; a logic 0 disables the output buffer.
Address:
Read:
Write:
Reset:
$0004
Bit 7
6
5
4
3
2
1
DDRA7 DDRA6 DDRA5 DDRA4 DDRA3 DDRA2 DDRA1
0
0
0
0
0
0
0
Figure 22-3. Data Direction Register A (DDRA)
Bit 0
DDRA0
0
DDRA[7:0] — Data Direction Register A Bits
These read/write bits control port A data direction. Reset clears DDRA[7:0], configuring all port A pins
as inputs.
1 = Corresponding port A pin configured as output
0 = Corresponding port A pin configured as input
NOTE
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.
Figure 22-4 shows the port A I/O logic.
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
250
Freescale Semiconductor