mc68hc05pl4b Freescale Semiconductor, Inc, mc68hc05pl4b Datasheet - Page 45

• Manufacturer Part Number: mc68hc05pl4b
• Description: Low-cost Single-chip Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

7.1
MC68HC05PL4
REV 2.0
This section describes the general purpose I/O ports on the MC68HC05PL4 and
MC68HC05PL4B MCUs.
In the MC68HC05PL4, 23 bidirectional I/O lines are available, arranged as one
7-bit I/O port (Port A), one 8-bit I/O port (Port B), and one 8-bit I/O port (Port C).
In the MC68HC05PL4B, 22 bidirectional I/O lines are available, arranged as one
6-bit I/O port (Port A), one 8-bit I/O port (Port B), and one 8-bit I/O port (Port C).
To avoid generating a glitch on an I/O port pin, data should be written to the I/O
port data register before writing a “1” (for output) to the corresponding data
direction register.
PARALLEL PORTS
Port A, B, and C are bidirectional ports. Each port pin is controlled by the
corresponding bits in a data direction register and a data register as shown in
Figure 7-1. The functions of the I/O pins are summarized in Table 7-1.
Read/Write DDR
Write Data
Read Data
RESET
(RST)
Freescale Semiconductor, Inc.
Figure 7-1. Port Input/Output Circuitry
For More Information On This Product,
INPUT/OUTPUT PORTS
Go to: www.freescale.com
INPUT/OUTPUT PORTS
Data Direction
Register Bit
Data
Register Bit
SECTION 7
April 30, 1998
NOTE
GENERAL RELEASE SPECIFICATION
OUTPUT
I/O PIN
7-1