NXP Semiconductors MPC5644A, Reference Manual, Page: 1623 / 1735

FlexRay Communication Controller (FlexRay)
MPC5644A Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor 1623
• When a slot occurs, if a slot is assigned to a node on a channel that node only transmits a frame on
that channel if there is data ready and there is a match on relevant transmit filters (no null frames
are sent).
The transmission of a frame in the dynamic segment is determined by the availability of data and the match
of the cycle counter filter of the transmit message buffer.
33.7.8.3.1 Transmit data not available
If transmit data are not available , that is, the transmit buffer is not committed FR_MBCCSR t [CMT] = 0
and/or locked FR_MBCCSR t [LCKS] = 1,
a) for the cycles in the set {4n}, which is assigned to both buffers, the receive buffer will be found
and the node can receive data, and
b) for the cycles in the set {4n + 2}, which is assigned to the receive buffer only, the receive buffer
will be found and the node can receive data.
The receive cycles are shown in Figure 33-163
Figure 33-163. Transmit data not available
33.7.8.3.2 Transmit data available
If transmit data are available , that is, the transmit buffer is committed FR_MBCCSR t [CMT] = 1 and not
locked FR_MBCCSR t [LCKS] = 0,
a) for the cycles in the set {4n}, which is assigned to both buffers, the transmit buffer will be found
and the node transmits data.
b) for the cycles in the set {4n + 2}, which is assigned to the receive buffer only, the receive buffer
will be found and the node can receive data.
The receive and transmit cycles are shown in Figure 33-163 .
Figure 33-164. Transmit data not available
0
RX
1 2
RX
3 4
RX
5 6
RX
7 59 60
RX
61 62
RX
8
RX
63
0
TX
1 2
RX
3 4
TX
5 6
RX
7 59 60
TX
61 62
RX
8
TX
63