MC68HC05P4A Datasheet, PDF (15/72 Pages) Advanced Analogic Technologies – Microcontrollers

Signal Description
1.6.4 RESET
This active low pin is used to reset the MCU to a known startup state by pulling RESET low. The RESET
pin contains an internal Schmitt trigger as part of its input to improve noise immunity.
1.6.5 TCMP
This pin provides an output for the output compare feature of the on-chip timer system.
1.6.6 PA0–PA7
Port A is an 8-bit bidirectional port which does not share any of its pins with other subsystems. The port
A data register is at $0000, and the data direction register is at $0004. Reset does not affect the data
registers, but clears the data direction registers, thereby returning the ports to inputs. Writing a 1 to a data
direction register (DDR) bit sets the corresponding port bit to output mode. Port A has mask option
enabled pullup devices and interrupt capability by pin. For a detailed description of I/O programming, refer
to 1.7 Input/Output Programming.
V_DD
V_DD
MASK OPTION
DDR BIT
IRQ
SCHMITT
TRIGGER
PA0
NORMAL PORT
CIRCUITRY
FROM ALL OTHER PORT A PINS
Figure 1-3. Port A Pullup Option
TO INTERRUPT
LOGIC
1.6.7 SDO/PB5, SDI/PB6, and SCK/PB7
Port B is a 3-bit bidirectional port. These pins are shared with the SIOP subsystem. Refer to Chapter 7
Simple Serial Input/Output Port (SIOP) for a detailed description of the SIOP. The address of the port B
data register is $0001, and the data direction register is at address $0005. 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.
1.6.8 PC0–PC7
Port C is an 8-bit bidirectional port which does not share any of its pins with other subsystems. The
address of the port C data register is $0002, and the DDR is at address $0006. 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. Two of the port C pins, PC0 and PC1, have a
higher current drive capability. See Chapter 12 Electrical Specifications.
MC68HC05P4A Data Sheet, Rev. 7.1
Freescale Semiconductor
15