mc68hc908gp32 Freescale Semiconductor, Inc, mc68hc908gp32 Datasheet - Page 118

• Manufacturer Part Number: mc68hc908gp32
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Input/Output (I/O) Ports
12.2 Port A
Port A is an 8-bit special-function port that shares all eight of its pins with the keyboard interrupt (KBI)
module. Port A also has software configurable pullup devices if configured as an input port.
12.2.1 Port A Data Register
The port A data register (PTA) contains a data latch for each of the eight port A pins.
PTA7–PTA0 — Port A Data Bits
KBD7–KBD0 — Keyboard Inputs
12.2.2 Data Direction Register A
Data direction register A (DDRA) 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.
DDRA7–DDRA0 — Data Direction Register A Bits
118
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.
The keyboard interrupt enable bits, KBIE7–KBIE0, in the keyboard interrupt control register (KBICR)
enable the port A pins as external interrupt pins.
These read/write bits control port A data direction. Reset clears DDRA7–DDRA0, configuring all port
A pins as inputs.
1 = Corresponding port A pin configured as output
0 = Corresponding port A pin configured as input
Alternate Function:
Address:
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.
Reset:
Read:
Write:
Reset:
Read:
Write:
DDRA7
$0000
$0004
Bit 7
0
PTA7
KBD7
Bit 7
Figure 12-3. Data Direction Register A (DDRA)
Figure 12-2. Port A Data Register (PTA)
DDRA6
6
0
PTA6
KBD6
MC68HC908GP32 Data Sheet, Rev. 10
6
DDRA5
5
0
PTA5
KBD5
5
NOTE
DDRA4
(see Chapter 10 Keyboard Interrupt (KBI)
4
0
Unaffected by reset
KBD4
PTA4
4
DDRA3
3
0
KBD3
PTA3
3
DDRA2
2
0
KBD2
PTA2
2
DDRA1
1
0
KBD1
PTA1
1
Freescale Semiconductor
DDRA0
Bit 0
0
KBD0
PTA0
Bit 0
Module)