
Slave LIN Interface Controller (SLIC) Module
MC68HC908QL4 MC68HC908QL3 MC68HC908QL2 Data Sheet, Rev. 4
156
Freescale Semiconductor
Figure 14-16. Handling Command Messages (Data Receive)
The SLIC transmit go (TXGO) bit should be 0 for command frames, indicating to the SLIC that data is
coming from the master. The checksum mode control (CHKMOD) bit allows the user to select which
method of checksum calculation is desired for this message frame. The LIN 1.3 checksum does not
include the identifier byte in the calculation, while the SAE version does include this byte. Because the
identifier is already received by the SLIC by this time, the default is to include it in the calculation. If a LIN
1.3 checksum is desired, a 1 in CHKMOD will reset the checksum circuitry to begin calculating the
COMMAND MESSAGE
PROCESS
VALID ID
N
Y
INITIALIZE SW BYTE COUNT
WRITE SLCDLC FOR THIS ID
0nxx xxxx
(TXGO = 0)
(CHKMOD = n)
PROCESS
REQUEST MESSAGE
EXTENDED FRAME
Y
N
EXIT ISR
ERROR CODE
Y
N
PROCESS ERROR CODE:
BYTE FRAMING ERROR
NO-BUS-ACTIVITY
EXIT ISR
RETURN TO IDLE
1. EMPTY RX BUFFER
2. DECREMENT SW BYTE COUNT BY 8
LAST FRAME
(SW BYTE COUNT £8)
Y
N
WRITE SLCDLC FOR THIS ID
0n00 0xxx
(TXGO = 0)
(CHKMOD = n)
EXIT ISR
ERROR CODE
Y
N
PROCESS ERROR CODE:
BYTE FRAMING ERROR
CHECKSUM-ERROR
NO-BUS-ACTIVITY
EXIT ISR
RETURN TO IDLE
EMPTY RX BUFFER
INTERRUPT
READ SLCSV
CLEAR SLCF
INTERRUPT
READ SLCSV
CLEAR SLCF
RECEIVE BUFFER OVERRUN
RECEIVE BUFFER OVERRUN