MC68HC908LJ24 Datasheet, PDF (381/464 Pages) Motorola, Inc – Microcontrollers

Freescale Semiconductor, Inc.
Input/Output (I/O) Ports
Port A
ADC[3:0] — ADC channels 0 to 3
ADC[3:0] are pins used for the input channels to the analog-to-digital
converter module. The channel select bits, ADCH[4:0], in the ADC
status and control register define which port pin will be used as an
ADC input and overrides any control from the port I/O logic. See
Section 16. Analog-to-Digital Converter (ADC).
NOTE:
Care must be taken when reading port A while applying analog voltages
to ADC[3:0] pins. If the appropriate ADC channel is not enabled,
excessive current drain may occur if analog voltages are applied to the
PTAx/ADCx pin, while PTA is read as a digital input. Those ports not
selected as analog input channels are considered digital I/O ports.
18.3.2 Data Direction Register A (DDRA)
Data direction register A 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: $0004
Bit 7
6
5
4
3
2
1
Read:
DDRA7 DDRA6 DDRA5 DDRA4 DDRA3 DDRA2 DDRA1
Write:
Reset: 0
0
0
0
0
0
0
Figure 18-3. Data Direction Register A (DDRA)
Bit 0
DDRA0
0
DDRA[7:0] — Data Direction Register A Bits
These read/write bits control port A data direction. Reset clears
DDRA[7:0], 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. Figure 18-4 shows
the port A I/O logic.
MC68HC908LJ24/LK24 — Rev. 2
MOTOROLA
Input/Output (I/O) Ports
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Data Sheet
381