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TC1784
Asynchronous/Synchronous Serial Interface (ASC)
User´s Manual
16-15
V1.1, 2011-05
ASC, V1.6
Using the Fractional Divider
When the fractional divider is selected, the input clock
f
DIV
for the baud rate timer is
derived from the module clock
f
ASC
by a programmable fractional divider. If
CON.FDE = 1, the fractional divider is activated. It divides
f
ASC
by a fraction of n/512 for
any value of n from 0 to 511. If n = 0, the divider ratio is 1, which means that
f
DIV
=
f
ASC
.
In general, the fractional divider allows the baud rate to be programmed with much better
accuracy than with the two fixed prescaler divider stages.
Note: In fractional divider mode, the clock
f
DIV
can have a maximum period jitter of one
f
ASC
clock period.
BG represents the content of the reload register bit field BG.BR_VALUE, taken as an
unsigned 13-bit integer. FDV represents the contents of the fractional divider register bit
field FDV.FD_VALUE, taken as an unsigned 9-bit integer.
Table 16-3
Asynchronous Baud Rate Formulas using the Fractional Input Clock
Divider
FDE
BRS
BG
FDV
Formula
1
–
0 … 8191 1 … 511
0
Table 16-4
Typical Asynchronous Baud Rates using the Fractional Input Clock
Divider
f
ASC
Desired
Baud Rate
BG
FDV
Resulting
Baud Rate
Deviation
90 MHz
115.2 kbit/s
0022
H
16F
H
115.199 kbit/s
0%
57.6 kbit/s
0045
H
16F
H
57.6 kbit/s
0%
38.4 kbit/s
0068
H
16F
H
38.4 kbit/s
0%
19.2 kbit/s
006A
H
0BB
H
57.6 kbit/s
0%
Baud rate
FDV
512
------------
f
ASC
16
BG 1
+
(
)
×
------------------------------------
×
=
Baud rate
f
ASC
16
BG 1
+
(
)
×
------------------------------------
=
Summary of Contents for TC1784
Page 1: ...User s Manual V1 1 2011 05 Microcontrollers TC1784 32 Bit Single Chip Microcontroller ...
Page 3: ...User s Manual V1 1 2011 05 Microcontrollers TC1784 32 Bit Single Chip Microcontroller ...
Page 950: ...TC1784 Direct Memory Access Controller DMA User s Manual 11 132 V1 1 2011 05 DMA V3 03 ...
Page 1949: ...TC1784 General Purpose Timer Array GPTA v5 User s Manual 21 297 V1 1 2011 05 GPTA v5 V1 14 ...
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