MC68HC908GZ8 Datasheet, PDF (202/344 Pages) Motorola, Inc – Microcontrollers

Input/Output (I/O) Ports
17.2 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.
17.2.1 Port A Data Register
The port A data register (PTA) contains a data latch for each of the eight port A
pins.
Address:
Read:
Write:
Reset:
Alternate
Function:
$0000
Bit 7
PTA7
KBD7
6
PTA6
KBD6
5
PTA5
KBD5
4
3
PTA4
PTA3
Unaffected by reset
KBD4
KBD3
2
PTA2
KBD2
Figure 17-2. Port A Data Register (PTA)
1
PTA1
KBD1
Bit 0
PTA0
KBD0
PTA7–PTA0 — 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.
KBD7–KBD0 — Keyboard Inputs
The keyboard interrupt enable bits, KBIE7–KBIE0, in the keyboard interrupt
control register (KBICR) enable the port A pins as external interrupt pins. See
Section 13. Keyboard Interrupt Module (KBI).
17.2.2 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.
Address:
Read:
Write:
Reset:
$0004
Bit 7
DDRA7
0
6
DDRA6
0
5
DDRA5
0
4
DDRA4
0
3
DDRA3
0
2
DDRA2
0
1
DDRA1
0
Figure 17-3. Data Direction Register A (DDRA)
Bit 0
DDRA0
0
Data Sheet
202
Input/Output (I/O) Ports
MC68HC908GZ8
Freescale Semiconductor