MC68HC05V12 Datasheet, PDF (85/246 Pages) Freescale Semiconductor, Inc – HCMOS Microcontreller Unit

Freescale Semiconductor, Inc.
Parallel Input/Output (I/O)
Port C
7.5.1 Port C Data Register
Each port C I/O pin has a corresponding bit in the port C data register.
When a port C pin is programmed as an output, the state of the
corresponding data register bit determines the state of the output pin.
When a port C pin is programmed as an input, any read of the port C
data register will return the logic state of the corresponding I/O pin. The
port C data register is unaffected by reset.
7.5.2 Port C Data Direction Register
Each port C I/O pin may be programmed as an input by clearing the
corresponding bit in the DDRC or programmed as an output by setting
the corresponding bit in the DDRC. The DDRC can be accessed at
address $0006 and is cleared by reset.
7.5.3 Port C I/O Pin Interrupts
The inputs of all eight bits of port C are ANDed into the IRQ input of the
CPU. See Figure 4-2. This port has its own interrupt request latch to
enable the user to differentiate between the IRQ sources. The port IRQ
inputs are falling edge sensitive only. Any port C pin can be disabled as
an interrupt input by setting the corresponding DDR bit or data register
bit. To enable port pin interrupts, the corresponding DDR and data
register bits must both be cleared. Any port C pin that is configured as
an output will not cause a port interrupt when the pin transitions from a
1 to a 0.
NOTE:
The BIH and BIL instructions will apply only to the level on the IRQ pin
itself and not to the internal IRQ input to the CPU. Therefore, BIH and
BIL cannot be used to obtain the result of the logical combination of the
eight pins of port C.
CAUTION:
Exercise caution when writing to the port C data register and data
direction register due to their interaction with the IRQ subsystem as
depicted in Figure 4-2. Special care should be exercised in using
read/modify/write instructions on these registers.
MC68HC05V12 — Rev. 2.0
Parallel Input/Output (I/O)
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Technical Data