MFR4300_07 Datasheet, PDF (159/266 Pages) Freescale Semiconductor, Inc – FlexRay Communication Controllers

FlexRay Module (FLEXRAYV2)
least one of the conditions mentioned above is fulfilled for these message buffers. The transition SA
changes the message buffer states from either Idle to CCSa or from HLck to HLckCCSa. In each case,
these message buffers will be used for null frame transmission in the next slot. A message buffer timing
and state change diagram for null frame transmission from Idle state is given in Figure 3-114.
SA
STS
Idle
MT ^start
MT ^start
search[s+1]
CCSa
slot s
CCNf
null frame transmit
slot s+1
Figure 3-114. Null Frame Transmission from Idle state
SSS
Idle
MT ^start
slot s+2
A message buffer timing and state change diagram for null frame transmission from HLck state is given
in Figure 3-115.
SA
HLck
HLckCCSa
MT ^start
MT ^start
search[s+1]
slot s
STS
HLckCCNf
null frame transmit
slot s+1
SSS
HLck
MT ^start
slot s+2
Figure 3-115. Null Frame Transmission from HLck state
If a transmit message buffer is in the CCSa or HLckCCSa state at the start of the transmission slot, a null
frame is transmitted in any case, even if the message buffer is unlocked or committed before the
transmission slot starts. A transmit message buffer timing and state change diagram for null frame
transmission for this case is given in Figure 3-116.
SA
HU
STS
HLck
HLckCCSa
MT ^start
MT ^start
search[s+1]
slot s
CCSa
CCNf
null frame transmit
slot s+1
SSS
Idle
MT ^start
slot s+2
Figure 3-116. Null Frame Transmission from HLck state with unlock
Since the null frame transmission will not use the message buffer data, the application can lock/unlock the
message buffer during null frame transmission. A transmit message buffer timing and state change
diagram for null frame transmission for this case is given in Figure 3-117.
MFR4300 Data Sheet, Rev. 3
Freescale Semiconductor
159