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CHAPTER 20 LIN-UART
Table 20.4-2 Function of Each Bit in Serial Mode Register (SMR)
No. Bit name Function
bit7,
bit6
MD1, MD0:
Operation mode setting bits
These two bits set the LIN-UART operation mode.
bit5 OTO:
One-to-one external clock input
enable bit
This bit sets an external clock directly to the LIN-UART serial clock by
writing "1".
This function is used for operating mode 2 (synchronous) slave mode
operation (ECCR:MS=1).
When EXT=0, this bit is fixed to "0".
bit4 EXT:
External serial clock source
selection bit
This bit selects the clock input.
When "0" is set to this bit, it selects the clock of internal baud rate generator
(reload counter). When "1" is set to it, it selects the external serial clock
source.
bit3 REST:
Restart of dedicated reload
counter bit
If a 1 is written to this bit, the reload counter is restarted. Writing 0 to it has
no effect.
Reading from this bit always returns 0.
bit2 UPCL :
LIN-UART programmable clear
bit (LIN-UART software reset)
Writing a 1 to this bit resets LIN-UART immediately (LIN-UART software
reset). The register settings are preserved. Possible reception or transmission
will cut off.
All flags (TDRE, RDRF, LBD, PE, ORE, FRE) are cleared. Reset the LIN-
UART after disabling the interrupt and transmission. Also, when the
reception data register is cleared (RDR = 00
H
), the reload counter restarts.
Writing 0 to this bit has no effect. Reading from it always returns 0.
bit1 SCKE:
LIN-UART serial clock output
enable bit
This bit controls the serial clock I/O ports.
When this bit is 0, SCKn pin operates as general-purpose I/O port or serial
clock input pin. When this bit is 1, the pin operates as serial clock output pin
and outputs clock in operating mode 2 (synchronous).
Note:
When using SCKn pin as serial clock input (SCKE=0) pin, set the
corresponding DDR bit of general-purpose port as input port. Also, select
external clock (EXT = 1) using the external clock selection bit.
Reference:
When the SCKn pin is assigned to serial clock output (SCKE=1), it functions
as the serial clock output pin regardless of the status of the general-purpose I/
O ports.
bit0 SOE:
LIN-UART serial data output
enable bit
This bit enables or disables the output of serial data.
When this bit is 0, SOTn pin operates as general-purpose I/O port. When this
bit is 1, SOTn pin operates as serial data output pins (SOTn).
Reference:
When the output of serial data is enabled (SOE=1), SOTn pin functions as
serial data output pin (SOTn) regardless of the status of general-purpose I/O
ports.