C509-L_97 SIEMENS [Siemens Semiconductor Group], C509-L_97 Datasheet - Page 166

• Manufacturer Part Number: C509-L_97
• Description: 8-Bit CMOS Microcontroller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

The baud rate generator consists of a free running upward counting 10-bit timer. On overflow of this
timer (next count step after counter value 3FF H ) there is an automatic 10-bit reload from the
registers S0RELL and S0RELH. The lower 8 bits of the timer are reloaded from S0RELL, while the
upper two bits are reloaded from bit 0 and 1 of register S0RELH. The baud rate timer is reloaded
by writing to S0RELL.
Special Function Register S0RELH (Address BA H )
Special Function Register S0RELL (Address AA H )
Bit
S0RELH.0-1
S0RELL.0-7
After reset S0RELH and S0RELL have a reload value of 3D9 H . With this reload value the baud rate
generator has an overflow rate of input clock / 39. With a 12-MHz oscillator frequency, the
commonly used baud rates 4800 baud (SMOD = 0) and 9600 baud (SMOD = 1) are available (with
0.16 % deviation).
With the baud rate generator as clock source for the serial port 0 in mode 1 and 3, the baud rate of
can be determined as follows:
At 12-MHz oscillator frequency a baud rate range from about 92 baud up to 375 kbaud is covered.
Semiconductor Group
Bit No.
AA H
BA H
Baud rate generator overflow rate = 2
MSB
Mode 1, 3 baud rate =
.7
–
7
7
.6
Function
Reload value. Upper two bits of the timer reload value.
Reload value. Lower 8 bit of timer reload value.
6
6
–
.5
5
–
5
64 x (baud rate generator overflow rate) x 2
.4
4
–
4
with S0REL = S0RELH.1 – 0, S0RELL.7 – 0
10
6-88
– S0REL
2
SMOD
.3
3
–
3
On-Chip Peripheral Components
x oscillator frequency
.2
2
–
2
MSB
.1
1
1
Reset Value : XXXXXX11 B
LSB
LSB
.0
0
0
Reset Value : D9 H
S0RELL
S0RELH
S0P
1997-10-01
C509-L