Asynchronous Serial Interface (Uart) Mode - NEC 78K0 User Manual

12.4.2 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 12-4).
<2> Set bits 1 to 4 (SL0, CL0, PS00, and PS01) of the ASIM0 register (see Figure 12-2).
<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 12-2. Relationship Between Register Settings and Pins
POWER0 TXE0 RXE0
0 0 0
1 0 1
1 0
1 1
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
250
CHAPTER 12 SERIAL INTERFACE UART0
PM10 P10 PM11
Note Note Note
× × ×
Note Note
× × 1
Note
0 1 ×
0 1 1
User's Manual U16227EJ2V0UD
P11 UART0
Operation
TxD0/SCK10/P10
Note
× Stop SCK10/P10
× Reception SCK10/P10
Note
× Transmission
× Transmission/
reception
Pin Function
RxD0/SI10/P11
SI10/P11
RxD0
TxD0 SI10/P11
TxD0 RxD0