SAB80515 Datasheet, PDF (52/270 Pages) Siemens Semiconductor Group – 8-Bit Single-Chip Microcontroller Family

On-Chip Peripheral Components
Figure 7-10
Special Function Register ADCON (Address 0D8H)
0DFH 0DEH 0DDH 0DCH 0DBH 0DAH 0D9H 0D8H
0D8H BD CLK ADEX BSY ADM MX2 MX1 MX0 ADCON
These bits are not used in controlling serial interface.
Bit
Function
BD
Baud rate enable.
When set, the baud rate in modes 1 and 3 of serial interface is taken from
a dedicated prescaler. Standard baud rates 4800 and 9600 baud at
12-MHz oscillator frequency can be achieved.
Using timer 1 to generate baud rates:
Timer 1 can be used for generating baud rates in mode 1 and 3 of the serial channel. Then the baud
rate is determined by the timer 1 overflow rate and the value of SMOD as follows:
2^SMOD
Mode 1, 3 baud rate =
x (Timer 1 OV-rate)
32
The timer 1 interrupt is usually disabled in this application. The timer itself can be configured for
either "timer" or "counter" operation, and in any of its operating modes. In the most typical
applications, it is configured for "timer" operation in the auto-reload mode (high nibble of
TMOD = 0010B). In the case, the baud rate is given by the formula:
2^SMOD x oscillator frequency
Mode 1, 3 baud rate =
32 x 12 x (256 – (TH1))
One can achieve very low baud rates with timer 1 by leaving the timer 1 interrupt enabled,
configuring the timer to run as 16-bit timer (high nibble of TMOD = 0001B), and using the timer 1
interrupt for a 16-bit software reload.
Table 7-4 lists various commonly used baud rates and shows how they can be obtained from
timer 1.
Semiconductor Group
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