PXS20RM Datasheet, PDF (833/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

FlexRay Communication Controller
SA
STS
Idle
MT ^start
MT ^start
search[s+1]
CCSa
slot s
CCNf
null frame transmit
slot s+1
Figure 26-133. 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 26-134.
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 26-134. 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 26-135.
SA
HU
HLck
HLckCCSa
MT ^start
MT ^start
search[s+1]
slot s
CCSa
STS
CCNf
null frame transmit
slot s+1
SSS
Idle
MT ^start
slot s+2
Figure 26-135. 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 26-136.
Freescale Semiconductor
PXS20 Microcontroller Reference Manual, Rev. 1
26-121