MC68HC908KX8 Datasheet, PDF (156/310 Pages) Motorola, Inc – Microcontrollers

Input/Output (I/O) Ports
TxD — SCI Transmit Data Output Bit
The PTB0/TxD pin is the transmit data output for the SCI module.
When the enable SCI bit, ENSCI, is clear, the SCI module is
disabled, and the PTB0/TxD pin is available for general-purpose I/O.
See Section 14. Serial Communications Interface Module (SCI).
AD3–AD0 — Analog-to-Digital Input Bits
AD3–AD0 are pins used for the input channels to the analog-to-digital
converter (ADC) module. The channel select bits in the ADC status
and control register define which port B pin will be used as an ADC
input and overrides any control from the port I/O logic by forcing that
pin as the input to the analog circuitry. See Section 17. Analog-to-
Digital Converter (ADC).
10.4.2 Data Direction Register B
Data direction register B (DDRB) determines whether each port B pin is
an input or an output. Writing a logic 1 to a DDRB bit enables the output
buffer for the corresponding port B pin; a logic 0 disables the output
buffer.
Address: $0005
Bit 7
6
5
4
3
2
1
Read:
DDRB7
Write:
DDRB6
DDRB5
DDRB4
DDRB3
DDRB2
DDRB1
Reset: 0
0
0
0
0
0
0
Figure 10-7. Data Direction Register B (DDRB)
Bit 0
DDRB0
0
DDRB7–DDRB0 — Data Direction Register B Bits
These read/write bits control port B data direction. Reset clears
DDRB7–DDRB0, configuring all port B pins as inputs.
1 = Corresponding port B pin configured as output
0 = Corresponding port B pin configured as input
NOTE: Avoid glitches on port B pins by writing to the port B data register before
changing data direction register B bits from 0 to 1.
Technical Data
156
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 — Rev. 1.0
Input/Output (I/O) Ports
MOTOROLA