mc9s12xf512 Freescale Semiconductor, Inc, mc9s12xf512 Datasheet - Page 581

• Manufacturer Part Number: mc9s12xf512
• Description: S12x Microcontrollers 16-bit Automotive Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

13.6.6.4.6
For double transmit message buffers, the message buffer search checks only the transmit side part. The
internal scheduling ensures, that the internal message transfer is stopped on the message buffer search start.
Thus, the transmit side of message buffer, that is not in its transmission or status update slot, is always in
the Idle state.
The message transmit behavior and transmission state changes of the transmit side of a double transmit
message buffer are the same as for single buffered transmit buffers, except that the transmit side of double
buffers can not be locked by the application, i.e. the HU and HL transition do not exist. Therefore, refer to
Section 13.6.6.2.5, “Message Transmission”
13.6.6.4.7
The message buffer status update behavior of the transmit side of a double transmit message buffer is the
same as for single transmit message buffers which is described in
Status Update”.
Additionally, the slot status field of the commit side is update after the update of the slot status field of the
transmit side, even if the commit side is locked by the application. This is implemented to provide the slot
status of the most recent transmission slot.
Freescale Semiconductor
Idle
HL
Message Transmission
Message Buffer Status Update
search[s+1]
HLck
Idle
Figure 13-129. Internal Message Transfer in Immediate Commit Mode
HU
slot s
Idle
MC9S12XF - Family Reference Manual, Rev.1.19
IS
CCITx
CCITx
IE
Idle
HL
Chapter 13 FlexRay Communication Controller (FLEXRAY)
HLck
Idle
slot s+1
Section 13.6.6.2.7, “Message Buffer
HU
Idle
overwrites non-transmitted message
internal message transfer
IS
CCITx
CCITx
IE
Idle
Idle
slot s+2
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