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XC161 Derivatives
Peripheral Units (Vol. 2 of 2)
Asynchronous/Synchronous Serial Interface (ASC)
User’s Manual
18-26
V2.2, 2004-01
ASC_X, V2.0
18.4.2
Baudrate in Synchronous Mode
For synchronous operation, the baudrate generator provides a clock with four times the
rate of the established baudrate (see
Figure 18-15 ASC Baudrate Generator Circuitry in Synchronous Mode
The baudrate for synchronous operation of serial channel ASC can be determined by the
formulas as shown in
Note: BG represents the contents of the reload bitfield BR_VALUE, taken as an
unsigned 13-bit integers.
The maximum baudrate that can be achieved in Synchronous Mode when using a
module clock of 40 MHz is 5 Mbit/s.
Table 18-7
Synchronous Baudrate Formulas
BRS
BG
Formula
0
0 … 8191
1
MCA05446
13-bit Reload Register
13-bit Baudrate Timer
f
BRT
f
DIV
MUX
2
3
R
f
ASC
BRS
Shift /
Sample
Clock
Selected Divider
2
3
BRS
0
1
4
Baudrate
f
ASC
8
BG
1
+
(
)
×
---------------------------------
=
BG
f
ASC
8
Baudrate
×
------------------------------------
1
–
=
Baudrate
f
ASC
12
BG
1
+
(
)
×
------------------------------------
=
BG
f
ASC
12
Baudrate
×
---------------------------------------
1
–
=