STR720 datasheet(207/401 Pages) STMICROELECTRONICS

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STR720 - CONTROLLER AREA NETWORK (CAN)

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This mode is provided for self-test functions. To be independent from external stimulation, the

CAN Core ignores acknowledge errors (recessive bit sampled in the acknowledge slot of a data/

remote frame) in Loop Back Mode. In this mode, the CAN Core performs an internal feedback

from its Tx output to its Rx input. The actual value of the CAN_RX input pin is disregarded by

the CAN Core. The transmitted messages can be monitored on the CAN_TX pin.

18.4.7

Loop Back Combined with Silent Mode

It is also possible to combine Loop Back Mode and Silent Mode by programming bits LBack

and Silent to one at the same time. This mode can be used for a “Hot Selftest”, which means

that CAN Peripheral can be tested without affecting a running CAN system connected to the

CAN_TX and CAN_RX pins. In this mode, the CAN_RX pin is disconnected from the CAN

Core and the CAN_TX pin is held recessive. Figure 32 shows the connection of signals

CAN_TX and CAN_RX to the CAN Core in case of the combination of Loop Back Mode with

Silent Mode.

Figure 31. CAN Core in Loop Back Mode

Figure 32. CAN Core in Loop Back Mode Combined with Silent Mode

CAN_TX CAN_RX

CAN Core

•

CAN Peripheral

CAN_TX

CAN_RX

CAN Core

•

CAN Peripheral

STR720 Datasheet(PDF) 207 Page - STMicroelectronics