SAF-C164SM Infineon Technologies, SAF-C164SM Datasheet - Page 225

• Manufacturer Part Number: SAF-C164SM
• Description: 16-Bit CMOS Microcontroller
• Manufacturer: Infineon Technologies

11.4
The serial channel ASC0 has its own dedicated 13-bit baud rate generator with 13-bit
reload capability, allowing baud rate generation independent of the GPT timers.
The baud rate generator is clocked with the CPU clock divided by 2 (
counts downwards and can be started or stopped through the Baud Rate Generator Run
Bit S0R in register S0CON. Each underflow of the timer provides one clock pulse to the
serial channel. The timer is reloaded with the value stored in its 13-bit reload register
each time it underflows. The resulting clock is again divided according to the operating
mode and controlled by the Baudrate Selection Bit S0BRS. If S0BRS = ‘1’, the clock
signal is additionally divided to 2/3
baud rate of ASC0 is determined by the CPU clock, the reload value, the value of S0BRS
and the operating mode (asynchronous or synchronous).
Register S0BG is the dual-function Baud Rate Generator/Reload register. Reading
S0BG returns the content of the timer (bits 15 … 13 return zero), while writing to S0BG
always updates the reload register (bits 15 … 13 are insignificant).
Each time S0BG is written to, an auto-reload of the timer with the content of the reload
register is performed. However, if S0R = ‘0’ at the time the write operation to S0BG is
performed, the timer will not be reloaded until the first instruction cycle after S0R = ‘1’.
Asynchronous Mode Baud Rates
For asynchronous operation, the baud rate generator provides a clock with 16 times the
rate of the established baud rate. Every received bit is sampled at the 7
cycle of this clock. The baud rate for asynchronous operation of serial channel ASC0 and
the required reload value for a given baudrate can be determined by the following
formulas:
<S0BRL> represents the contents of the reload register taken as unsigned 13-bit integer,
<S0BRS> represents the value of bit S0BRS (either ‘0’ or ‘1’), taken as integer.
The tables below list various commonly used baud rates and the required reload values
and deviation errors compared to the intended baud rates for a number of CPU
frequencies.
Note: The deviation errors given in the tables below are rounded. Using a baudrate
User’s Manual
B
S0BRL = (
Async
crystal (such as 18.432 MHz) will provide correct baud rates without deviation
errors.
=
16
16
ASC0 Baud Rate Generation
(2 + <S0BRS>)
(2 + <S0BRS>)
f
CPU
f
CPU
(<S0BRL> + 1)
B
rd
Async
of its frequency (see formulas and table). So the
Asynchronous/Synchronous Serial Interface
) - 1
11-11
C164CM/C164SM
f
CPU
th
/2). The timer
Derivatives
V1.0, 2002-02
, 8
th
and 9
th