
MC68HC05C8A
—
Rev. 3.0
General Release Specification
MOTOROLA
Input/Output (I/O) Ports
49
L
G
R
General Release Specification — MC68HC05C8A
Section 7. Input/Output (I/O) Ports
7.1 Contents
7.2
7.3
7.4
7.5
7.6
7.7
Introduction...............................................................................49
Port A........................................................................................49
Port B........................................................................................50
Port C........................................................................................50
Port D........................................................................................51
Input/Output Programming .......................................................51
7.2 Introduction
The MC68HC05C8A has three 8-bit input/output (I/O) ports.These 24
port pins are programmable as either inputs or outputs under software
control of the data direction registers. Port D does not have a data
direction register, and its seven pins are input only with the exception of
certain SCI/SPI functions.
NOTE:
To avoid a glitch on the output pins, write data to the I/O port data
register before writing a one to the corresponding data direction register.
7.3 Port A
Port A is an 8-bit bidirectional port which does not share any of its pins
with other subsystems. The port A data register is at $0000 and the data
direction register (DDR) is at $0004. Reset does not affect the data
registers, but clears the data direction registers, thereby returning the
ports to inputs. Writing a 1 to a DDR bit sets the corresponding port bit
to output mode.