
Chapter 13 FlexRay Communication Controller (FLEXRAY)
MC9S12XF - Family Reference Manual, Rev.1.19
Freescale Semiconductor
613
Furthermore the assumption is that both message buffers are enabled (MBCCSRt[EDS] = 1 and
MBCCSRr[EDS] = 1)
NOTE
The cycle set {4n+2} = {2,6,10, ...} is assigned to the receive buffer only.
The cycle set {4n} = {0,4,8,12, ...} is assigned to both buffers.
13.7.6.2
Behavior in static segment
In this case, both message buffers are assigned to a slot S in the static segment.
The conguration of a transmit buffer for a static slot S assigns this slot to the node as a transmit slot. The
FlexRay protocol requires:
When a slot occurs, if the slot is assigned to a node on a channel that node must transmit either a
normal frame or a null frame on that channel. Specically, a null frame will be sent if there is no
data ready, or if there is no match on a transmit lter (cycle counter ltering, for example).
Regardless of the availability of data and the cycle counter lter, the node will transmit a frame in the static
slot S. In any case, the result of the message buffer search will be the transmit message buffer t. The receive
message buffer r will not be found, no reception is possible.
13.7.6.3
Behavior in dynamic segment
In this case, both message buffers are assigned to a slot S in the dynamic segment. The FlexRay protocol
requires:
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 lters (no null frames
are sent).
Table 13-118. Receive Buffer Conguration
Register
Field
Value
Description
MBCCSRr
MCM
-
n/a
MBT
-
n/a
MTD
0
receive buffer
MBCCFr
MTM
-
n/a
CHA
1
assigned to channel A
CHB
0
not assigned to channel B
CCFE
1
cycle counter lter enabled
CCFMSK
000001
cycle set = {2n} = {0,2,4,6, ... }
CCFVAL
000000
MBFIDRr
FID
S
subscribed slot