MC68HC705P6A Datasheet, PDF (54/130 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Input/Output Ports
6.5 Port C
Port C is an 8-bit bidirectional port which can share pins PC3–PC7 with
the A/D subsystem. The port C data register is located at address $0002
and its data direction register (DDR) is located at address $0006. The
contents of the port C data register are indeterminate at initial powerup
and must be initialized by user software. Reset does not affect the data
registers, but clears the DDRs, thereby setting all of the port pins to input
mode. Writing a 1 to a DDR bit sets the corresponding port pin to output
mode (see Figure 6-3).
Port C may be used for general I/O applications when the A/D
subsystem is disabled. The ADON bit in register ADSC is used to
enable/disable the A/D subsystem. Care must be exercised when using
pins PC0–PC2 while the A/D subsystem is enabled. Accidental changes
to bits that affect pins PC3–PC7 in the data or DDR registers will produce
unpredictable results in the A/D subsystem. See Section 9. Analog
Subsystem.
READ $0006
WRITE $0006
WRITE $0002
RESET
(RST)
DATA DIRECTION
REGISTER BIT
DATA
REGISTER BIT
I/O
OUTPUT
PIN
READ $0002
INTERNAL HC05
DATA BUS
Figure 6-3. Port C I/O Circuitry
Advance Information
54
Input/Output Ports
MC68HC705P6A — Rev. 2.0
MOTOROLA