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CHAPTER 8 APPLICATIONS OF SERIAL INTERFACE
Table 8-10. Relations between Main System Clock and Baud Rate (at f
X
= 4.19 MHz)
MCS = 1
MCS = 0
Set value of BRGC
Error (%)
Set value of BRGC
Error (%)
75
0BH
1.14
EBH
1.14
110
03H
–2.01
E3H
–2.01
150
EBH
1.14
DBH
1.1.4
300
DBH
1.14
CBH
1.14
600
CBH
1.14
BBH
1.14
1200
BBH
1.14
ABH
1.14
2400
ABH
1.14
9BH
1.14
4800
9BH
1.14
8BH
1.14
9600
8BH
1.14
7BH
1.14
19200
7BH
1.14
6BH
1.14
31250
71H
–1.31
61H
–1.31
38400
6BH
1.14
5BH
1.14
76800
5BH
1.14
–
–
Remark
MCS: bit 0 of the oscillation mode select register (OSMS)
(c) Transmission
Transmission is started when transmit data has been written to the transmit shift register (TXS). The start
bit and parity bit are automatically appended.
(d) Reception
Reception is enabled when bit 6 (RXE) of the asynchronous serial interface mode register (ASIM) is set to
1, and the data input to the RxD pin is sampled. When reception of one frame of data has been completed,
the receive data in the shift register is transferred to the receive buffer register (RXB) and a receive end interrupt
request (INTSR) occurs.
(e) Receive error
During reception, three types of errors may occur: parity error, framing error, and overrun error. If the error
flag of the asynchronous serial interface status register (ASIS) is set as a result of data reception, a receive
error interrupt (INTSER) occurs. By reading the contents of ASIS in the receive error interrupt processing
(INTSER), which error has occurred can be identified. The contents of ASIS are reset (0) by either reading
the receive buffer register (RXB) or receiving the next data. (if the next data includes an error, that error flag
is set).
Cautions 1. The contents of the asynchronous serial interface status register (ASIS) are reset to 0
when the receive buffer register (RXB) is read or the next data is received. To determine
the nature of the error, be sure to read ASIS before reading RXB.
2. Be sure to read the receive buffer register (RXB) when a reception error has occurred.
Otherwise, an overrun error will occur when the next data is received, and the reception
error status will persist.
Baud rate (bps)