MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor
21-39
Figure 21-26. DMA Transfer of a RX frame
21.4.10.4 LIN Error Handling
The LIN hardware can detect several error conditions of the LIN protocol. LIN hardware will receive every
byte that was transmitted, and compare it with the intended values. If there is a mismatch, a bit error is
issued, and the LIN FSM will return to its start state.
For a RX frame the LIN hardware can detect a slave timeout error. The exact slave timeout error value can
be set via the timeout bits in the ESCI
x
_LTR. If the frame is not complete within the number of clock
cycles specified in the register, the LIN FSM will return to its start state, and the STO interrupt is issued.
The LIN protocol supports a sleep mode. After 25,000 bus cycles of inactivity the bus is assumed to be in
sleep mode. Normally entering sleep mode can be avoided, if the LIN master is regularly creating some
bus activity. Otherwise the timeout state needs to be detected by the application software, for example by
setting a timer.
Both LIN masters and LIN slaves can cause the bus to exit sleep mode by sending a break signal. The LIN
hardware will generate such a break, when WU bit in the LIN control register is written. After transmitting
this break the LIN hardware will not send out data (that is not raise the TXRDY flag) before the wake-up
delimiter period has expired. This period can be selected by setting the WUD bits in the LIN control
register.
Break signals sent by a LIN slave are received by the LIN hardware, and so indicated by setting the WAKE
flag in the LIN status register.
A physical bus error (LIN bus is permanently stuck at a fixed value) will set several error flags. If the input
is permanently low, the eSCI will set the framing error (FE) flag in the eSCI status register. If the RXD
input remains stuck at a fixed value for 31 RT clock cycles, after a transmission has started, the LIN
hardware will set the PBERR flag in the LIN status register. In addition a bit error may be generated.
Break
Sync
ID
Data
Data
CSum
• • •
LIN Frame
Transmit
DMA
Controller
Data n
Data 1
Timeout
Control/Timeout
Length
ID
•
•
•
TX DMA
Channel
LIN eSCI
Receive
From Master
From Slave
RX DMA
Channel
Register
Register
Summary of Contents for MPC5553
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