mfr4200 Freescale Semiconductor, Inc, mfr4200 Datasheet - Page 155

• Manufacturer Part Number: mfr4200
• Description: Flexray Communication Controllers
• Manufacturer: Freescale Semiconductor, Inc

3.4.1.5
The host commits a transmit message buffer for transmission by setting the BUFCMT flag of the
corresponding buffer to ‘1’.
The CC checks the BUFCMT bit of all transmit message buffers when it schedules a transmission.
The CC can transmit, or put a frame from a transmit message buffer into a transmission schedule, only
when the buffer is committed for transmission (BUFCMT = 1), unlocked (LOCK = 0), and all internal
procedures on that transmit message buffer are finished (copying process, unlock process, a transmission).
At the end of buffer transmission, The CC clears the BUFCMT bits of single transmit message buffers and
CC part buffers of double transmit message buffers committed for transmission.
The CC clears the BUFCMT bit of a double buffer’s host part at the end of the buffer copy process. During
the buffer copy process, the CC copies buffer data from the buffer’s CC part to the buffer’s host part.
The host may set the BUFCMT bit only for a locked transmit message buffer. To complete the commit
operation, the host must unlock the buffer. Thereafter, the CC indicates a successful commitment with the
BUFCMT set. The read operation of a BUFCMT bit always returns a ‘0’ for a locked buffer.
1 – The transmit message buffer is committed for transmission.
0 – The transmit message buffer is not committed for transmission.
3.4.1.6
ChA and ChB are channel filtering bits associated with each buffer. They serve as a filter for a receive
message buffer, and as a control field for a transmit message buffer.
Receive message buffer:
Received frames are stored if they are received on all the specified channels in the channel filtering field.
Other filtering criteria must also be met.
Freescale Semiconductor
BUFCMT — Message Buffer Commit Flag
ChA, ChB — Channel A and Channel B Flags
•
•
This flag is related only to transmit message buffers. Reading or writing to
BUFCMT bit in a receive message buffer has no meaning (i.e., this bit is not
used). When the host writes ‘1’ to the BUFCMT bit, that value will be stored
until the CC clears it; so, only one write is necessary. Writing a ‘0’ to the
BUFCMT location does not change its state.
Unlocking the buffer in the FIFO moves the FIFO buffer access pointer
to the next buffer in the FIFO (see
Function”). So, the FIFO does not support multiple consecutive
locking/unlocking of the same FIFO entry.
The host locks the FIFO buffers by setting the LOCK bit in FIFO buffer
number 0.
MFR4200 Data Sheet, Rev. 0
Message Buffer Control, Configuration, Status and Filtering Register Set
NOTE
Section 3.6, “Receive FIFO
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