Motorola MC68HC05RC8 User Manual
MC68HC05RC16 — Rev. 3.0
General Release Specification
MOTOROLA
Parallel Input/Output (I/O)
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General Release Specification — MC68HC05RC16
Section 7. Parallel Input/Output (I/O)
7.1 Contents
7.2 Introduction
In user mode, 20 lines (in 28-pin PDIP or SOIC) or 24 lines (in 44-lead
PLCC) are arranged as three 8-bit I/O ports. These ports are
programmable as either inputs or outputs under software control of the
data direction registers.
PLCC) are arranged as three 8-bit I/O ports. These ports are
programmable as either inputs or outputs under software control of the
data direction registers.
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.
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
register, but clears the data direction register, thereby returning the ports
to inputs. Writing a one to a DDR bit sets the corresponding port bit to
output mode.
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
register, but clears the data direction register, thereby returning the ports
to inputs. Writing a one to a DDR bit sets the corresponding port bit to
output mode.