MC68HC05SR3D Datasheet, PDF (27/96 Pages) Freescale Semiconductor, Inc – Microcontrollers

3
3
INPUT/OUTPUT PORTS
The MC68HC05SR3 has 32 bidirectional I/O lines, arranged as four 8-bit I/O ports (Port A, B, C,
and D). The individual bits in these ports are programmable as either inputs or outputs under
software control by the Data Direction Registers (DDRs). All port pins each has an associated
20KΩ pull-up resistor, which can be connected/disconnected under software control. Also, each
port pin is capable of sinking and driving a maximum current of 10mA (e.g. direct drive for LEDs).
Port A can also be configured for keyboard interrupts.
3.1
Parallel Ports
Port A, B, C, and D are 8-bit bidirectional ports. Each Port pin is controlled by the corresponding
bits in a Data Direction Register and a Data Register as shown in Figure 3-1. The functions of the
I/O pins are summarized in Table 3-1.
Table 3-1 I/O Pin Functions
R/W 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.
3.1.1 Port Data Registers
Each Port I/O pin has a corresponding bit in the Port Data Register. When a Port I/O pin is
programmed as an output the state of the corresponding data register bit determines the state of
the output pin. All Port I/O pins can drive a current of 10mA when programmed as outputs. When
a Port pin is programmed as an input, any read of the Port Data Register will return the logic state
of the corresponding I/O pin. The locations of the Data Registers for Port A, B, C, and D are at
$00, $01, $02, and $03 respectively. The Port Data Registers are unaffected by reset.
MC68HC05SR3
INPUT/OUTPUT PORTS
TPG
Freescale
3-1