MC68HC05P4A Datasheet, PDF (16/72 Pages) Advanced Analogic Technologies – Microcontrollers

General Description
1.6.9 PD5 and TCAP/PD7
Port D is a 2-bit port. PD5 is I/O and TCAP/PD7 is input-only shared with the timer input capture. The
address of the port D data register is $0003, and the data direction register is at address $0007. 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. The TCAP/PD7 pin
controls the input capture feature for the on-chip programmable timer. This pin can be read at any time
even if the TCAP function is enabled.
1.7 Input/Output Programming
Port pins may be programmed as inputs or outputs under software control. The direction of the pins is
determined by the state of the corresponding bit in the port data direction register (DDR). Each I/O port
has an associated DDR. Any I/O port pin is configured as an output if its corresponding DDR bit is set to
a logic 1. A pin is configured as an input if its corresponding DDR bit is cleared to a logic 0.
At power-on or reset, all DDRs are cleared, which configures all pins as inputs. The data direction
registers are capable of being written to or read by the processor. During the programmed output state,
a read of the data register actually reads the value of the output data latch and not the I/O pin. For further
information, see Table 1-1 and Figure 1-4.
Table 1-1. I/O Pin Functions
R/W^{(1) DDR}
I/O Pin Function
0
0 The I/O pin is in input mode. Data is written into the output data latch.
0
1 Data is written into the output data latch and output to the I/O pin.
1
0 The state of the I/O pin is read.
1
1 The I/O pin is in an output mode. The output data latch is read.
1. R/W is an internal signal.
DATA DIRECTION
REGISTER BIT
LATCHED OUTPUT
DATA BIT
I/O
OUTPUT
PIN
INPUT
REG
BIT
INPUT
I/O
Figure 1-4. I/O Circuitry
MC68HC05P4A Data Sheet, Rev. 7.1
16
Freescale Semiconductor