Datasheet

Input/Output Ports (PORTS)
MC68HC908QY/QT Family Data Sheet, Rev. 6
98 Freescale Semiconductor
12.2.1 Port A Data Register
The port A data register (PTA) contains a data latch for each of the six port A pins.
PTA[5:0] — 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.
AWUL — Auto Wakeup Latch Data Bit
This is a read-only bit which has the value of the auto wakeup interrupt request latch. The wakeup
request signal is generated internally (see Chapter 4 Auto Wakeup Module (AWU)). There is no PTA6
port nor any of the associated bits such as PTA6 data register, pullup enable or direction.
KBI[5:0] — Port A Keyboard Interrupts
The keyboard interrupt enable bits, KBIE5–KBIE0, in the keyboard interrupt control enable register
(KBIER) enable the port A pins as external interrupt pins (see Chapter 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 1
to a DDRA bit enables the output buffer for the corresponding port A pin; a 0 disables the output buffer.
DDRA[5:0] — Data Direction Register A Bits
These read/write bits control port A data direction. Reset clears DDRA[5:0], 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.
Address:
$0000
Bit 76 5 4 3 2 1Bit 0
Read:
R
AWUL
PTA5 PTA4 PTA3
PTA2
PTA1 PTA0
Write:
Reset: Unaffected by reset
Additional Functions:
KBI5 KBI4 KBI3 KBI2 KBI1 KBI0
R = Reserved
= Unimplemented
Figure 12-1. Port A Data Register (PTA)
Address:
$0004
Bit 7654321Bit 0
Read:
R R DDRA5 DDRA4 DDRA3
0
DDRA1 DDRA0
Write:
Reset:00000000
R= Reserved
= Unimplemented
Figure 12-2. Data Direction Register A (DDRA)