TC1784
FlexRay™ Protocol Controller (E-Ray)
User´s Manual
20-258
V1.1, 2011-05
E-Ray, V3.13
20.8
Restrictions
The following restrictions have to be considered when programming the E-Ray IP-
module. A violation of these restrictions may lead to an erroneous behavior of the E-Ray
IP-module.
20.8.1
Message Buffers with the same Frame ID
If two or more Message Buffers are configured with the same Frame ID, and if they have
a matching cycle counter filter value for the same slot, then the Message Buffer with the
lowest Message Buffer number is used.
Sharing of a static time slot via cycle counter filtering between different nodes of a
FlexRay™ network is
not
allowed.
20.8.2
Data Transfers between IBF / OBF and Message RAM
The time required to transfer the contents of a Message Buffer between IBF / OBF and
Message RAM depends on the setup time to start the first transfer, the number of 4-byte
words to be transferred, and the number of concurrent tasks to be managed by the
Message Handler. The number of 4-byte words varies from 4 (Header Section only) to
68 ( maximum Data Section) while the number of concurrent task varies from
one to three.
The following concurrent tasks are executed under control of the Message Handler:
•
Data transfer between IBF or OBF and Message RAM
•
Data transfer between TBF1 and Message RAM, search next TX / RX Message
Buffer CHA
•
Data transfer between TBF2 and Message RAM, search next TX / RX Message
Buffer CHB
Transfers between IBF and Message RAM respectively Message RAM and OBF can
only be handled one after another. In case that e.g. a transfer between IBF and Message
RAM has been started shortly before a transfer between Message RAM and OBF is
requested, the OBF transfer has to wait until the IBF transfer has completed.
The relative time is measured in
f
CLC_ERAY
cycles. Absolute time depends on the actual
f
CLC_ERAY
cycle period.
cyclestrans = (remaining cycles of transfer running) + (cycles of requested transfer)
cyclestrans = cyc cyclesreq
cyclesrem = (number of concurrent tasks) * (setup time + (number of 4-byte words)rem)
cyclesreq = (number of concurrent tasks) * (setup time + (number of 4-byte words)req)
setup time = 2
f
CLC_ERAY
cycles
Under worst case conditions a transfer is requested directly after the previous transfer
started:
Summary of Contents for TC1784
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