C508_01 Datasheet, PDF (174/267 Pages) Infineon Technologies AG – 8-Bit CMOS Microcontroller

C508
On-Chip Peripheral Components
Special Function Register SRELH (Address BA_H)
Special Function Register SRELL (Address AA_H)
Bit No. MSB
7
6
5
4
3
2
BA_H
–
–
–
–
–
–
Reset Value: XXXXXX11_B
Reset Value: D9_H
LSB
1
0
MSB
.9
.8
SRELH
AA_H
.7
.6
.5
.4
.3
.2
.1
LSB
.0
SRELL
The shaded bits are not used for reload operation.
Bit
SRELH.0-1
SRELL.0-7
–
Function
Baudrate generator reload high value
Upper two bits of the baudrate timer reload value.
Baudrate generator reload low value
Lower 8 bits of the baudrate timer reload value.
Reserved bits for future use. Read by CPU returns undefined
values.
After reset, SRELH and SRELL have a reload value of 3D9_H. With this reload value, the
baudrate generator has an overflow rate of (input clock)/39. With 10 MHz oscillator
frequency, a reload value of 37E_H is required to achieve the commonly used baudrates
of 4800 baud (SMOD = 0) and 9600 baud (SMOD = 1) at a deviation of 0.16%.
With the baudrate generator as clock source for the serial port in Modes 1 and 3, the
baudrate can be determined as follows:
Mode 1, 3 baudrate =
2^SMOD × oscillator frequency
16 × (baudrate generator overflow rate)
Baudrate generator overflow rate = 2¹⁰ - SREL
with SREL = SRELH.1 - 0, SRELL.7 - 0
User’s Manual
6-109
2001-05