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M451
May. 4, 2018
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NewDat remains set.
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When the transmission completed successfully, bit NewDat is cleared.
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When a transmission fails (lost arbitration or error), bit NewDat remains set.
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To restart the transmission, the software should set the bit TxRqst again.
6.20.6 Test Mode
Test Mode is entered by setting the Test bit (CAN_CON[7]). In Test Mode, bits Tx1 (CAN_TEST[6]),
Tx0 (CAN_TEST[5]), LBack (CAN_TEST[4]), Silent (CAN_TEST[3]) and Basic (CAN_TEST[2]) are
writeable. Bit Rx (CAN_TEST[7]) monitors the state of the CAN_RX pin and therefore is only readable.
All Test Register functions are disabled when the Test bit is cleared.
Silent Mode
6.20.6.1
The CAN Core can be set in Silent Mode by programming the Silent bit (CAN_TEST[3]) to one. In
Silent Mode, the C_CAN is able to receive valid data frames and valid remote frames, but it sends
only recessive bits on the CAN bus and it cannot start a transmission. If the CAN Core is required to
send a dominant bit (ACK bit, Error Frames), the bit is rerouted internally so that the CAN Core
monitors this dominant bit, although the CAN bus may remain in recessive state. The Silent Mode can
be used to analysis the traffic on a CAN bus without affecting it by the transmission of dominant bits.
The Figure 6.20-2 shows the connection of signals CAN_TX and CAN_RX to the CAN Core in Silent
Mode.
C_CAN
= 1
CAN_TX
CAN_RX
CAN_Core
Tx
Rx
Figure 6.20-2 CAN Core in Silent Mode
Loop Back Mode
6.20.6.2
The CAN Core can be set in Loop Back Mode by programming the Test Register bit LBack
(CAN_TEST[4]) to one. In Loop Back Mode, the CAN Core treats its own transmitted messages as
received messages and stores them in a Receive Buffer (if they pass acceptance filtering). The Figure
6.20-3 shows the connection of signals, CAN_TX and CAN_RX, to the CAN Core in Loop Back Mode.