MC68HC908JG16 Datasheet, PDF (259/324 Pages) Motorola, Inc – Microcontrollers

Input/Output (I/O) Ports
Port A
AD7–AD0 — Analog-to-Digital Input Pins
AD7–AD0 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 (ADSCR) define which port A pin will be
used as an ADC input and overrides any control from the port I/O or
keyboard interrupt logic. (See Section 13. Analog-to-Digital
Converter (ADC).)
14.3.2 Data Direction Register A
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
Write:
DDRA6
DDRA5
DDRA4
DDRA3
DDRA2
DDRA1
Reset: 0*
0
0
0
0
0
0
* DDRA7 bit is reset by POR or LVI reset only.
Figure 14-3. 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 14-4 shows the port A I/O logic.
MC68HC908JG16 — Rev. 1.1
Freescale Semiconductor
Input/Output (I/O) Ports
Technical Data
259