FUJITSU MB91460 SERIES FR60 - Manual (Page 738)

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Chapter 34 CAN Controller
3.Functional Description
Figure 3-2 CAN Core in Loop Back Mode
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 at the CAN_TX pin.
3.7 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”, meaning the CAN can be tested without
affecting a running CAN system connected to the pins CAN_TX and CAN_RX. In this mode the CAN_RX pin
is disconnected from the CAN Core and the CAN_TX pin is held recessive.
Figure 3-3 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 3-3 CAN Core in Loop Back combined with Silent Mode
3.8 Basic Mode
The CAN Core can be set in Basic Mode by programming the Test Register bit Basic to one. In this mode the
CAN module runs without the Message RAM.