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I/O PORT
This chapter explains the function and operation of the I/O port.
8.1 Overview of I/O Port
I/O ports can be used as general-purpose I/O ports (parallel I/O ports). In the MB90420/5 (A) series, there
are nine ports (58 pins). Each port pin also serves as a resource I/O pin.
n I/O Port function
The I/O ports enable to output data to the I/O pins from the CPU and fetch signals input to the I/O pins to the
CPU using the port data register (PDR). And the I/O ports can set any direction for the I/O pins bit-by-bit by
using the port direction register (DDR). The following shows the function of each port, and the resources
that it also serves as:
• Port 0: Serves as both general-purpose I/O port and resource (External interrupt input pin/UART/PPG)
• Port 1: Serves as both general-purpose I/O port and resource (PPG/reload timer/watch timer/ICU)
• Port 3: Serves as both general-purpose I/O port and resource (LCD)
• Port 4: Serves as both general-purpose I/O port and resource (LCD)
• Port 5: Serves as both general-purpose I/O port and resource (external interrupt input pin/CAN/sound
generator)
• Port 6: Serves as both general-purpose I/O port and resource (analog input pin)
• Port 7: Serves as both general-purpose I/O port and resource (SMC)
• Port 8: Serves as both general-purpose I/O port and resource (SMC)
• Port 9: Serves as both general-purpose I/O port and resource (LCD)
Table 8-1 lists the functions of each port.
8-3
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