UPSD3422_06 Datasheet, PDF (103/293 Pages) STMicroelectronics – Turbo Plus Series Fast Turbo 8032 MCU with USB and Programmable Logic

uPSD34xx
Serial UART interfaces
21.3.1
21.3.2
Using timer 1 to generate baud rates
When Timer 1 is used as the baud rate generator (bits RCLK = 0, TCLK = 0), the baud rates
in Modes 1 and 3 are determined by the Timer 1 overflow rate and the value of SMOD as
follows:
Mode 1,3 Baud Rate =
(2^SMOD / 32) x (Timer 1 overflow rate)
The Timer 1 Interrupt should be disabled in this application. The Timer itself can be
configured for either “timer” or “counter” operation, and in any of its 3 running modes. In the
most typical applications, it is configured for “timer” operation, in the Auto-reload Mode (high
nibble of the SFR TMOD = 0010B). In that case the baud rate is given by the formula:
Mode 1,3 Baud Rate =
(2^SMOD / 32) x (f_OSC / (12 x [256 – (TH1)]))
Table 49 lists various commonly used baud rates and how they can be obtained from Timer
1.
Using timer/counter 2 to generate baud rates
See Section 20.6.3: Baud rate generator mode on page 94.
Table 49. Commonly used baud rates generated from timer 1
Timer 1
UART Mode
f_OSC MHz
Desired
Baud
Rate
Resultant Baud
Baud
Rate
Rate Deviation
SMOD
bit in
PCON
C/T Bit
in
TMOD
Timer
Mode
in
TMOD
TH1
Reload
value
(hex)
Mode 0 Max 40.0 3.33MHz 3.33MHz
0
X
X
X
X
Mode 2 Max 40.0
1250 k 1250 k
0
1
X
X
X
Mode 2 Max 40.0
625 k
625 k
0
0
X
X
X
Modes 1 or 3 40.0
19200 18939 -1.36%
1
0
2
F5
Modes 1 or 3 40.0
9600
9470
-1.36%
1
0
2
EA
Modes 1 or 3 36.0
19200 18570 -2.34%
1
0
2
F6
Modes 1 or 3 33.333 57600 57870 0.47%
1
0
2
FD
Modes 1 or 3 33.333 28800 28934 0.47%
1
0
2
FA
Modes 1 or 3 33.333 19200 19290 0.47%
1
0
2
F7
Modes 1 or 3 33.333 9600
9645
0.47%
1
0
2
EE
Modes 1 or 3 24.0
9600
9615
0.16%
1
0
2
F3
Modes 1 or 3 12.0
4800
4808
0.16%
1
0
2
F3
Modes 1 or 3 11.0592 57600 57600
0
1
0
2
FF
Modes 1 or 3 11.0592 28800 28800
0
1
0
2
FE
Modes 1 or 3 11.0592 19200 19200
0
1
0
2
FD
Modes 1 or 3 11.0592 9600
9600
0
1
0
2
FA
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