TC1784
FlexRay™ Protocol Controller (E-Ray)
User´s Manual
20-27
V1.1, 2011-05
E-Ray, V3.13
The cycle counter value of Frames send in ATM mode can be programmed via
MTCCV.CCV (writable in ATM and loop back mode only).
Loop Back Mode
The loop back mode is entered by writing 1111
B
to the CHI Command Vector
SUCC1.CMD in the SUC Configuration Register 1 (CHI command: LOOP_BACK) while
the Communication Controller is in “CONFIG” state and bit TEST1.WRTEN in the Test
Register 1 is set. This write operation has to be directly preceded by two consecutive
write accesses to the Configuration Lock Key (unlock sequence). When called in any
other state or when bit TEST1.WRTEN is not set, SUCC1.CMD will be reset to
0000
B
= “COMMAND_NOT_ACCEPTED”. CCSV.POCS in the Communication
Controller Status Vector will show 0000 1101
H
while the E-Ray module is in loop back
mode.
Loop Back mode can be left by writing 0001
B
(CHI command: “CONFIG”) to the CHI
Command Vector SUCC1.CMD in the SUC Configuration Register 1.
The loop back test mode is intended to check the module’s internal data paths. Normal,
time triggered operation is not possible in loop back mode.
There are two possibilities to perform a loop back test. External loop back via physical
layer (TEST1.ELBE = 1) or internal loop back for in-system self-test (TEST1.ELBE = 0).
In case of an internal loop back pins TXENA, TXENB are in their inactive state, pins
TXDA and TXDB are set to HIGH, pins RXDAn and RXDBn are not evaluated.
When the Communication Controller is in loop back mode, a loop back test is started by
the Host writing a message to the Input Buffer and requesting the transmission by writing
to the Input Buffer Command Request register IBCR. The Message Handler will transfer
the message into the Message RAM and then into the Transient Buffer of the selected
channel. The Channel Protocol Controller (PRT) will read (in 32-bit words) the message
from the transmit part of the Transient Buffer and load it into its Rx / Tx shift register. The
serial transmission is looped back into the shift register; its content is written into the
receive part of the channels’s Transient Buffer before the next word is loaded.
The PRT and the Message Handler will then treat this transmitted message like a
received message, perform an acceptance filtering on Frame ID and receive channel,
and store the message into the Message RAM if it passed acceptance filtering. The loop
back test ends with the Host requesting this received message from the Message RAM
and then checking the contents of the Output Buffer.
Each FlexRay™ channel is tested separately. The E-Ray cannot receive messages from
the FlexRay™ bus while it is in the loop back mode.
The cycle counter value of Frames used in loop back mode can be programmed via
MTCCV.CCV (writable in ATM and loop back mode only).
Note that in case of an odd payload the last two bytes of the looped-back payload will be
shifted by 16 bits to the right inside the last 32-bit data word.
Содержание TC1784
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