XC164-16 Datasheet, PDF (255/417 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller with C166SV2 Core Volume 2 (of 2): Peripheral Units

XC164-16 Derivatives
Peripheral Units (Vol. 2 of 2)
Asynchronous/Synchronous Serial Interface (ASC)
In general, the baudrate generator in Asynchronous Mode is build up by two parts (see
also Figure 19-14):
• The clock prescaler part which derives f_DIV from f_ASC
• The baudrate timer part which generates the sample clock f_BRT and the baudrate
clock f_BR
Prior to an Autobaud Detection the prescaler part has to be set up by the CPU while the
baudrate timer (register ASCx_BG) is initialized with a 13-bit value (BR_VALUE)
automatically after a successful autobaud detection. For the following calculations, the
fractional divider is used (FDE = 1).
Note: It is also possible to use the fixed divide-by-2 or divide-by-3 prescaler. But the
fractional divider allows the much more precise adaption of f_DIV to the required
value.
Standard Baudrates
For standard baudrate detection the baudrates as shown in Table 19-8 can be e.g.
detected. Therefore, the output frequency f_DIV of the baudrate generator must be set to
a frequency derived from the module clock f_ASC in a way that it is equal to 11.0592 MHz.
The value to be written into register FDV is the nearest integer value which is calculated
according the following formula:
FDV = -5---1---2-----^×-----1---1---.--0----5---9---2-----M-----H-----z-
f_ASC
(19.1)
Table 19-8 defines the nine standard baudrates (Br0 - Br8) which can be detected for
f_DIV = 11.0592 MHz.
Table 19-8 Autobaud Detection Using Standard Baudrates (f_DIV = 11.0592 MHz)
Baudrate Detectable Standard Divide Factor d_f BG is Loaded after
Numbering Baudrate
Detection with Value
Br0
230.400 kbit/s
48
Br1
115.200 kbit/s
96
Br2
57.600 kbit/s
192
Br3
38.400 kbit/s
288
Br4
19.200 kbit/s
576
Br5
9600 bit/s
1152
Br6
4800 bit/s
2304
Br7
2400 bit/s
4608
Br8
1200 bit/s
9216
2 = 002_H
5 = 005_H
11 = 00B_H
17 = 011_H
35 = 023_H
71 = 047_H
143 = 08F_H
287 = 11F_H
575 = 23F_H
User’s Manual
ASC_X, V2.0
19-30
V2.1, 2004-03