STR720 datasheet(206/401 Pages) STMICROELECTRONICS

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STR720 - CONTROLLER AREA NETWORK (CAN)

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18.4.5

Silent Mode

The CAN Core can be set in Silent Mode by programming the Silent bit in the Test Register to

one.

In Silent Mode, the CAN Peripheral 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 analyse the traffic on a CAN bus without

affecting it by the transmission of dominant bits. Figure 30 shows the connection of signals

CAN_TX and CAN_RX to the CAN Core in Silent Mode.

In ISO 11898-1, Silent Mode is called Bus Monitoring Mode.

18.4.6

Loop Back Mode

The CAN Core can be set in Loop Back Mode by programming the Test Register bit LBack 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). Figure 31

shows the connection of signals, CAN_TX and CAN_RX, to the CAN Core in Loop Back

Mode.

Figure 30. CAN Core in Silent Mode

CAN_TX

CAN_RX

CAN Core

CAN Peripheral

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STR720 数据表(PDF) 206 Page - STMicroelectronics