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CHAPTER 4 I/O PORTS
4.1 Overview of I/O Ports
The I/O ports consist of five ports (33 pins) including N-ch open-drain and CMOS
general-purpose I/O ports (parallel I/O ports).
The ports also serve as peripherals (I/O pins of peripheral functions).
■ I/O port functions
The functions of the I/O ports are to output data from the CPU via the I/O pins and to fetch signals input to
the I/O pins into the CPU. Input and output are performed via the port data registers (PDR). Also, for
certain ports the direction of each I/O pin can be individually set to either input or output for each bit by the
port data direction register (DDR).
The following lists the functions of each port and the peripheral with which the ports also serve as.
• Port 0: General-purpose N-ch open-drain I/O port. Also serves as LCD segment driver pins.
• Port 1: General-purpose N-ch open-drain I/O port. Also serves as LCD segment driver pins.
• Port 2: General-purpose N-ch open-drain I/O port. Also serves as LCD segment driver pins.
• Port 3: General-purpose N-ch open-drain I/O port. Also serves as LCD bias pins.
• Port 4: General-purpose CMOS I/O port. Also serves as other peripheral I/O pins.
Table 4.1-1 "Port function" lists the functions of each port and Table 4.1-2 "Port registers" lists the
registers for each port.
Table 4.1-1 Port function
Port Pin name
Input
type
Output
type
Function Bit 7Bit 6Bit 5Bit 4Bit 3Bit 2Bit 1Bit 0
Port 0
P00/SEG20
to
P07/SEG27
CMOS
N-ch
open-drain
General-purpose I/O port P07 P06 P05 P04 P03 P02 P01 P00
Segment driver output SEG27 SEG26 SEG25 SEG24 SEG23 SEG22 SEG21 SEG20
Port 1
P10/SEG28
to
P17/SEG35
General-purpose I/O port P17 P16 P15 P14 P13 P12 P11 P10
Segment driver output SEG35 SEG34 SEG33 SEG32 SEG31 SEG30 SEG29 SEG28
Port 2
P20/SEG36
to
P25/SEG41
General-purpose I/O port -- -- P25 P24 P23 P22 P21 P20
Segment driver output -- -- SEG41 SEG40 SEG39 SEG38 SEG37 SEG36
Port 3
P30
to
P33/V2
General-purpose I/O port -- -- -- -- P33 P32 P31 P30
LCD bias -- -- -- -- V2 V1 -- --
Port 4
P40
to
P46/INT0
CMOS
(resource:
hysteresis)
CMOS
(push-pull
option)
General-purpose I/O port -- P46 P45 P44 P43 P42 P41 P40
Peripherals -- INT0 SCK SO SI
PWC/
INT1
PWM --