mc68hc05l25 Freescale Semiconductor, Inc, mc68hc05l25 Datasheet - Page 64

• Manufacturer Part Number: mc68hc05l25
• Description: M68hc05 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Input/Output Ports (I/O)
7.4 Port C
Port C is a 4-bit I/O port which shares its pins with external interrupt IRQ and the serial peripheral interface
(SPI) system as shown in
corresponding bits in a wired-OR mode register and a pullup register. The port C data register is located
at address $0002. The port C pullup register (RCR) is located at address $0009 of the option map. The
wired-OR mode register (WOMR) is located at address $000A of the option map. Reset clears the RCR
and the WOMR.
The PC0–PC2 pins are shared with the serial peripheral interface (SPI). When the SPI is enabled (SPE
= 1), the pins PC0, PC1, and PC2 are configured as serial clock output or input (SCK), serial data output
(SDO), and serial data input (SDI) pins, respectively. The direction of the SCK depends on the MSTR bit
in the SPCR. When PORTC is read, the pin state is read. See
pin should be at the V
The PC3 pin is shared with the external interrupt IRQ pin. The IRQ pin has a Schmitt trigger to improve
noise immunity. The PC3 pin state can be read any time regardless of the IRQ configurations.
Port C bits 2 and 3, when configured as output ports, are open drain outputs.
64
INTERNAL HC05
DATA BUS
WRITE OPTN: $0009
WRITE OPTN: $000A
WRITE OPTN: $0002
WRITE $0002
READ OPTN: $000A
READ OPTN: $0009
READ OPTN: $0002
READ $0002
DD
level before the SPI is enabled.
RESET
Figure 7-13
(RST)
Figure 7-13. Port PC0/SCK Circuitry
DATA DIRECTION
MC68HC05L25 Data Sheet, Rev. 3.1
REGISTER BIT
REGISTER BIT
REGISTER BIT
REGISTER BIT
OPEN DRAIN
through
PULLUP
DATA
SYSTEM
SPI
Figure
SCK OUT
SCK IN
MSTR
7-16. Each port C pin is controlled by the
Table 7-9
PULLUP
OUTPUT
LOGIC
through
OUTPUT
Table
Freescale Semiconductor
7-10. The SCK
R PULLUP
PIN
I/O