MC68HC05V12 Datasheet, PDF (82/246 Pages) Freescale Semiconductor, Inc – HCMOS Microcontreller Unit

Freescale Semiconductor, Inc.
Parallel Input/Output (I/O)
7.3 Port A
Port A is a 7-bit bidirectional port which functions as shown in
Figure 7-1. Each pin is controlled by the corresponding bit in a data
direction register and a data register. The port A data register (PORTA)
is located at address $0000. The port A data direction register (DDRA)
is located at address $0004. Reset clears DDRA. The port A data
register is unaffected by reset.
READ $0004
WRITE $0004
WRITE $0000
READ $0000
DATA DIRECTION
REGISTER BIT
DATA
REGISTER BIT
I/O
OUTPUT
PIN
INTERNAL HC05
DATA BUS
RESET
(RST)
Figure 7-1. Port A I/O Circuitry
7.3.1 Port A Data Register
Each port A I/O pin has a corresponding bit in the port A data register.
When a port A pin is programmed as an output, the state of the
corresponding data register bit determines the state of the output pin.
When a port A pin is programmed as an input, any read of the port A data
register will return the logic state of the corresponding I/O pin. The port
A data register is unaffected by reset.
Technical Data
Parallel Input/Output (I/O)
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MC68HC05V12 — Rev. 2.0