MC9S08EL32 Datasheet, PDF (212/356 Pages) Freescale Semiconductor, Inc – 8-Bit HCS08 Central Processor Unit (CPU)

unmasked, after 8 bytes are received or an error is detected. At this interrupt, the SLCSV will indicate an
error condition (in case of byte framing error, idle bus) or that the receive buffer is full. If the data is
successfully received, the user must then empty the buffer by reading SLCD7-SLCD0 and then subtract 8
from the software byte count. When this software counter reaches 8 or fewer, the remaining data bytes will
fit in the buffer and only one interrupt should occur. At this time, the final interrupt may be handled
normally, continuing to use the software counter to read the proper number of bytes from the appropriate
SLCD registers.
NOTE
Do not write SLCDLC more than one time per LIN message frame. The
SLIC tracks the number of sent or received bytes based on the value written
to this register at the beginning of the data field and rewriting this register
will corrupt the checksum calculation and cause unpredictable behavior in
the SLIC module. The application software must track the number of sent
or received bytes to know what the current byte count in the SLIC is. If
programming in C, make sure to use the VOLATILE modifier on this
variable (or make it a global variable) to ensure that it keeps its value
between interrupts.
12.6.8.3 Possible Errors on Command Message Data
Possible errors on command message data are:
• Byte Framing Error
• Checksum-Error (LIN specified error)
• No-Bus-Activity (LIN specified error)
• Receiver Buffer Overrun Error
12.6.9 Handling Request LIN Message Frames
Figure 12-16 shows how to handle request message frames, where the SLIC module is sending data to the
master node.
Request message frames refer to LIN messages frames where the master node is “requesting” the slave
node to supply information. The implication is that the slave will then be transmitting data to the master
for this message frame. This can be a standard LIN message frame of 1–8 data bytes, a reserved LIN
system message (using 0x3D identifier), or an extended request message frame utilizing the reserved 0x3E
identifier or perhaps the 0x3F LIN reserved extended identifier. The SLIC module is capable of handling
request message frames containing up to 64 bytes of data, while still automatically calculating and/or
verifying the checksum.
12.6.9.1 Standard Request Message Frames
Dealing with request messages with the SLIC is very similar to dealing with command messages, with one
important difference. Because the SLIC is now to be transmitting data in the LIN message frame, the user
software must load the data to be transmitted into the message buffer prior to initiating the transmission.
MC9S08EL32 Series and MC9S08SL16 Series Data Sheet, Rev. 3
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