V C L K
a
T
d
M
P
b it
T
ú
û
ù
ê
ë
é
+
÷
ø
ö
ç
è
æ
+
+
=
1 6
1
1 6
VCLK
i
T
d
M
P
bit
T
ú
û
ù
ê
ë
é
+
÷
ø
ö
ç
è
æ
+
+
=
16
1
16
SCICLK Frequency
=
Asynchronous baud value
=
For P = 0,
Asynchronous baud value
=
VCLK Frequency
P
1
M
16
------
+
+
----------------------------------------------------
SCICLK Frequency
16
----------------------------------------------------------
VCLK Frequency
32
-------------------------------------------------
SCI Communication Formats
1236
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Serial Communication Interface (SCI)/ Local Interconnect Network (LIN)
Module
In asynchronous timing mode, the SCI generates a baud clock according to the following formula:
(38)
25.2.3.1 Superfractional Divider, SCI Asynchronous Mode
The superfractional divider is available in SCI asynchronous mode (idle-line and address-bit mode).
Building on the 4-bit fractional divider M (BRS[27:24]), the super fractional divider uses an additional 3-bit
modulating value, illustrated in
. The bits with a 1 in the table will have an additional VCLK
period added to their T
bit
. If the character length is more than 10, then the modulation table will be a rolled-
over version of the original table (
), as shown in
The baud rate will vary over a data field to average according to the BRS[30:28] value by a “
d
” fraction of
the peripheral internal clock:
0<d<1.
Refer
for a simple Average “d’ calculation based on “U”
value (BRS[30:28]).
The instantaneous bit time is expressed in terms of
T
VCLK
as follows:
For all P other than 0, and all M and d (0 or 1),
(39)
For P = 0 T
bit
= 32T
VCLK
The averaged bit time is expressed in terms of
T
VCLK
as follows:
For all P other than 0, and all M and d (0<d<1),
(40)
For P = 0 T
bit
= 32T
VCLK
(1)
Normal configuration = Start + 8 Data Bits + Stop Bit
Table 25-1. Superfractional Bit Modulation for SCI Mode (Normal Configuration)
(1)
BRS[30:28]
Start Bit
D[0]
D[1]
D[2]
D[3]
D[4]
D[5]
D[6]
D[7]
Stop Bit
0h
0
0
0
0
0
0
0
0
0
0
1h
1
0
0
0
0
0
0
0
1
0
2h
1
0
0
0
1
0
0
0
1
0
3h
1
0
1
0
1
0
0
0
1
0
4h
1
0
1
0
1
0
1
0
1
0
5h
1
1
1
0
1
0
1
0
1
1
6h
1
1
1
0
1
1
1
0
1
1
7h
1
1
1
1
1
1
1
0
1
1
