UPSD33XX Datasheet, PDF (84/231 Pages) STMicroelectronics – Fast 8032 MCU with Programmable Logic

uPSD33xx
UART Baud Rates
The baud rate in Mode 0 is fixed:
Mode 0 Baud Rate = f_OSC / 12
The baud rate in Mode 2 depends on the value of
the bit SMOD in the SFR named PCON. If SMOD
= 0 (default value), the baud rate is 1/64 the oscil-
lator frequency, f_OSC. If SMOD = 1, the baud rate
is 1/32 the oscillator frequency.
Mode 2 Baud Rate = (2^SMOD / 64) x f_OSC
Baud rates in Modes 1 and 3 are determined by
the Timer 1 or Timer 2 overflow rate.
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 applica-
tions, 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 47 lists various commonly used baud rates
and how they can be obtained from Timer 1.
Using Timer/Counter 2 to Generate Baud
Rates. See
Baud
Rate
Generator
Mode, page 77.
Table 47. Commonly Used Baud Rates Generated from Timer 1
UART Mode
f_OSC MHz
Desired
Baud Rate
Resultant
Baud Rate
Baud Rate
Deviation
SMOD
bit in
PCON
C/T Bit
in TMOD
Timer 1
Timer
TH1
Mode in Reload
TMOD 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
Modes 1 or 3
3.6864
19200
19200
0
1
0
2
FF
Modes 1 or 3
3.6864
9600
9600
0
1
0
2
FE
Modes 1 or 3
1.8432
9600
9600
0
1
0
2
FF
Modes 1 or 3
1.8432
4800
4800
0
1
0
2
FE
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