MC68HC908GR16 Datasheet, PDF (132/310 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Input/Output Ports (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.
Address:
Read:
Write:
Reset:
Alternate
Function:
$0000
Bit 7
PTA7
KBD7
6
5
4
3
2
PTA6
PTA5
PTA4
PTA3
PTA2
Unaffected by reset
KBD6
KBD5
KBD4
KBD3
KBD2
Figure 12-2. 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 9. Keyboard Interrupt Module (KBI).
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.
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 12-3. Data Direction Register A (DDRA)
DDRA7–DDRA0 — Data Direction Register A Bits
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
Bit 0
DDRA0
0
Data Sheet
132
Input/Output Ports (PORTS)
For More Information On This Product,
Go to: www.freescale.com
MC68HC908GR16 — Rev. 1.0
MOTOROLA