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CHAPTER 13 SERIAL INTERFACE UART0
User’s Manual U16228EJ2V0UD
282
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
PM10
P10
PM11
P11
UART0
Operation
TxD0/SCK10/P10
RxD0/SI10/P11
0
0
0
×
Note
×
Note
×
Note
×
Note
Stop
SCK10/P10
SI10/P11
0
1
×
Note
×
Note
1
×
Reception
SCK10/P10
RxD0
1
0
0
1
×
Note
×
Note
Transmission
TxD0
SI10/P11
1
1
1
0
1
1
×
Transmission/
reception
TxD0
RxD0
Note
Can be set as port function.
Remark
×:
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