www
.mcu.com.cn
199
/
239
Rev.
1.00
CMS80F731x Reference Manual
BRTCKDIV is a BRT timer prescale selection bit, set by the register BRTCON. That is, the value of the BRT at the
corresponding baud rate should be set to:{BRTDH,BRTDL}
{BRTDH,BRTDL}=65536-
Fsys×2
SMODn
32×2
BRTCKDIV
×BaudRate
22.3.3
Baud Rate Error
In mode 1 and mode 3, UARTn selects different baud rate clock sources, and the errors at different baud rates are as
follows:
Table 1) and 2) are some of the baud rate information in the 8-bit automatic reload mode of timer 1/timer 4 in variable baud
rate mode. Table 3) and 4) show the BRT timer overflow rate in variable baud rate mode as part of the baud rate information of
the UART clock source.
1
)
SMODn=0
,
T1M=1/T4M=1
baud
rate
Fsys=8MHz
Fsys=16MHz
Fsys=24MHz
Fsys=48MHz
Kbps
{TH1,
TH4}
Current
Rate
%
Error
{TH1,
TH4}
Current
Rate
%
Error
{TH1,
TH4}
Current
Rate
%
Error
{TH1,
TH4}
Current
Rate
%
Error
4800
243
4808
-0.16
230
4808
-0.16
217
4808
-0.16
178
4808
-0.16
9600
--
--
--
247
9615
-0.16
236
9375
2.34
217
9615
-0.16
19200
--
--
--
--
--
--
246
18750
2.34
236
18750
2.34
38400
--
--
--
--
--
--
251
37500
2.34
246
37500
2.34
115200
--
--
--
--
--
--
--
--
--
--
--
--
250000
--
--
--
--
--
--
--
--
--
--
--
--
500000
--
--
--
--
--
--
--
--
--
--
--
--
2
)
SMODn=1
,
T1M=1/T4M=1
baud
rate
Fsys=8MHz
Fsys=16MHz
Fsys=24MHz
Fsys=48MHz
Kbps
{TH1,
TH4}
Current
Rate
%
Error
{TH1,
TH4}
Current
Rate
%
Error
{TH1,
TH4}
Current
Rate
%
Error
{TH1,
TH4}
Current
Rate
%
Error
4800
230
4808
-0.16
204
4808
-0.16
178
4808
-0.16
100
4808
-0.16
9600
243
9615
-0.16
230
9615
-0.16
217
9615
-0.16
178
9615
-0.16
19200
--
--
--
243
19230
-0.16
236
18750
2.34
217
19231
-0.16
38400
--
--
--
--
--
--
246
37500
2.34
236
37500
2.34
115200
--
--
--
--
--
--
--
--
--
--
--
--
250000
--
--
--
--
--
--
--
--
--
--
--
--
500000
--
--
--
--
--
--
--
--
--
--
--
--