Datasheet

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CHAPTER 13 SERIAL INTERFACE UART0

User’s Manual U18698EJ1V0UD

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13.4.2 Asynchronous serial interface (UART) mode

In this mode, 1-byte data is transmitted/received following a start bit, and a full-duplex operation can be performed.

A dedicated UART baud rate generator is incorporated, so that communication can be executed at a wide range of

baud rates.

(1) Registers used

• Asynchronous serial interface operation mode register 0 (ASIM0)

• Asynchronous serial interface reception error status register 0 (ASIS0)

• Baud rate generator control register 0 (BRGC0)

• Port mode register 1 (PM1)

• Port register 1 (P1)

The basic procedure of setting an operation in the UART mode is as follows.

<1> Set the BRGC0 register (see Figure 13-4).

<2> Set bits 1 to 4 (SL0, CL0, PS00, and PS01) of the ASIM0 register (see Figure 13-2).

<3> Set bit 7 (POWER0) of the ASIM0 register to 1.

<4> Set bit 6 (TXE0) of the ASIM0 register to 1. → Transmission is enabled.

Set bit 5 (RXE0) of the ASIM0 register to 1. → Reception is enabled.

<5> Write data to the TXS0 register. → Data transmission is started.

Caution Take relationship with the other party of communication when setting the port mode register

and port register.

The relationship between the register settings and pins is shown below.

Table 13-2. Relationship Between Register Settings and Pins

Pin Function POWER0 TXE0 RXE0 PM13 P13 PM12 P12

UART0

Operation

TxD0/KR4/P13/<TxD6> RxD0/KR3/P12/<RxD6>

0 0 0 ×

Note

Stop KR4/P13/<TxD6> KR3/P12/<RxD6>

0 1 ×

Note

Reception KR4/P13 RxD0

1 0 0

Note

Transmission TxD0 KR3/P12

1 1 0

Transmission/

reception

TxD0 RxD0

Note Can be set as port function, key interrupt, or serial interface UART6 (only when UART0 is stopped).

Remarks 1. ×: don’t care

POWER0: Bit 7 of asynchronous serial interface operation mode register 0 (ASIM0)

TXE0: Bit 6 of ASIM0

RXE0: Bit 5 of ASIM0

PM1×: Port mode register

P1×: Port output latch

2. The functions within arrowheads (< >) can be assigned by setting the input switch control register

(ISC).