Freescale Semiconductor, Inc.
Input/Output (I/O) Ports
Port A
13.3 Port A
Port A is an 8-bit special function port that shares six of its pins with the
keyboard interrupt module (KBD). PTA6–PTA1 contain pullup resistors
enabled when the port pin is enabled as a keyboard interrupt. Port A pins
are also high-current port pins with 3-mA sink capabilities.
13.3.1 Port A Data Register
The port A data register (PTA) contains a data latch for each of the eight
port A pins.
Address: $0000
Bit 7
6
5
4
3
2
1
Bit 0
Read:
PTA7
Write:
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
Reset:
Unaffected by reset
KBD4 KBD3
Alternate
Function:
KBD6
KBD5
KBD2
KBD1
= Unimplemented
Figure 13-2. 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.
KBD[6:1] — Keyboard Wakeup Pins
The keyboard interrupt enable bits, KBIE[6:1], in the keyboard
interrupt control register enable the port A pin as external interrupt
pins and related internal pullup resistor. See Section 14.
Keyboard/External Interrupt Module (KBI).
NOTE: The enabling of a keyboard interrupt pin will overide the corresponding
definition of the pin in the data direction register. However, the data
direction register bit must be a logic 0 for software to read the pin.
MC68HC908RFRK2
MOTOROLA
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Input/Output (I/O) Ports
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