SDA5252 SIEMENS [Siemens Semiconductor Group], SDA5252 Datasheet - Page 94

• Manufacturer Part Number: SDA5252
• Description: TVTEXT 8-Bit Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

Semiconductor Group
6.3.10.2
The baud rate in mode 0 is fixed:
The baud rate in mode 2 depends on the value of bit SMOD in special function register
PCON (bit 7). If SMOD = 0 (which is the value on reset), the baud rate is 1/32 of the
oscillator frequency. If SMOD = 1, the baud rate is 1/16 of the oscillator frequency.
The baud rates in modes 1 and 3 are determined by the timer 1 overflow rate or can be
generated by the internal baud rate generator.
When timer 1 is used as the baud rate generator, the baud rates in modes 1 and 3 are
determined by the timer 1 overflow rate and the value of SMOD as follows:
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 the 3 running modes.
In the most typical applications, it is configured for “timer” operation, in the auto-reload
mode (high nibble of TMOD = 0010B). In that case, the baud rate is given by the formula:
One can achieve very low baud rates with timer 1 by leaving the timer 1 interrupt
enabled, configuring the timer to run as a 16-bit timer (high nibble of TMOD = 0001B),
and using the timer 1 interrupt to do a 16-bit software reload.
Mode 2 baud rate
Mode 1, 3 baud rate
Mode 0 baud rate
Mode 1, 3 baud rate
Baud Rates
=
=
2
----------------- -
=
--------------
=
f
SMOD
OSC
6
32
2
----------------- -
2
----------------- -
SMOD
SMOD
16
16
f
OSC
Time 1 overflow
---------------------------------------------
12
256 TH1
f
OSC
94
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SDA 525x
1998-04-08