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CHAPTER 20 UART2, UART3
20.7.3
Operation with LIN Function (Operation Mode 3)
UART2, UART3 can be used either as LIN-Master or LIN-Slave. For this LIN function a
special mode is provided. Setting the UART2, UART3 to mode 3 configures the data
format to 8N1-LSB-first format.
■ Operation in Asynchronous LIN Mode (Operation Mode 3)
●
UART2, UART3 as LIN master
In LIN master mode the master determines the baud rate of the whole sub bus, therefore slave devices have
to synchronize to the master. Therefore the desired baud rate remains fixed in master operation after
initialization.
Writing a "1" into the LBR bit of the Extended Communication Control Register (ECCR2/ECCR3)
generates a 13 - 16 bit time low-level on the SOT2/SOT3 pin, which is the LIN synchronization break and
the start of a LIN message. Thereby the TDRE flag of the Serial Status Register (SSR2/SSR3) goes "0". If
valid data does not exist in the transmission data register (TDR2/TDR3), this bit is reset to "1" after the
break, and generates a transmission interrupt for the CPU (if TIE of SSR2/SSR3 is "1").
The length of the Synchronization break to be sent can be determined by the LBL1/LBL0 bits of the
ESCR2/ESCR3 as follows:
Table 20.7-2 LIN Break Length
LBL1
0
0
1
1
The Synch Field is sent as byte data of 55
just after writing the "1" to the LBR bit, although the TDRE flag is "0".
388
LBL0
Length of Break
0
13 Bit times
1
14 Bit times
0
15 Bit times
1
16 Bit times
after the LIN break. The 55
H
can be written to the TDR2/TDR3
H
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