PXS20RM Datasheet, PDF (894/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

FlexRay Communication Controller
Register
FR_MBCCFRr
FR_MBFIDRr
Table 26-138. Receive Buffer Configuration (continued)
Field
Value
Description
MTM
CHA
CHB
CCFE
CCFMSK
CCFVAL
FID
-
1
0
1
000001
000000
S
n/a
assigned to channel A
not assigned to channel B
cycle counter filter enabled
cycle set = {2n} = {0,2,4,6,...}
subscribed slot
Furthermore the assumption is that both message buffers are enabled (FR_MBCCSRt[EDS] = 1 and
FR_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.
26.7.7.2 Behavior in static segment
In this case, both message buffers are assigned to a slot S in the static segment.
The configuration 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. Specifically, a null frame will be sent if there is no
data ready, or if there is no match on a transmit filter (cycle counter filtering, for example).
Regardless of the availability of data and the cycle counter filter, 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.
26.7.7.3 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 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.
26-182
PXS20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor