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
LIN
1646
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
Serial Communication Interface (SCI)/ Local Interconnect Network (LIN)
Module
29.3.1.4.2 Superfractional Divider
The superfractional divider scheme applies to the following modes:
•
LIN master mode (synch field + identifier field + response field + checksum field)
•
LIN slave mode (response field + checksum field)
29.3.1.4.3 Superfractional Divider In LIN Mode
Building on the 4-bit fractional divider M (BRS[27:24], the superfractional divider uses an additional 3-bit
modulating value, illustrated in
. The sync field (0x55), the identifier field and the response field
can all be seen as 8-bit data bytes flanked by a start bit and a stop bit. The bits with a 1 in the table will
have an additional VCLK period added to their T
bit
.
(1)
1. In LIN master mode bit modulation applies to synch field + identifier field + response field
2. In LIN slave mode bit modulation applies to identifier field + response field
Table 29-7. Superfractional Bit Modulation for LIN Master Mode and Slave Mode
(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
The baud rate will vary over a LIN data field to average according to the BRS[30:28] value by a
d
fraction
of the peripheral internal clock: 0<d<1.
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),
(47)
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),
(48)
For P = 0 T
bit
= 32T
VCLK
With the superfractional divider, a LIN baud rate of 20 kbps is achievable with an internal clock VCLK of
726 kHz. Furthermore, a rate of 400 kbps is achievable with an VCLK of 14.6 MHz.