7630 datasheet(115/238 Pages) RENESAS

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7630 Group User’s Manual

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2-49

2.4 Controller Area Network (CAN) module

• Lock the following registers to prevent accidental modifications: (1) acceptance code and mask registers

(CACi/CAMi, Figures 2.4.6 to 2.4.15), (2) CAN bus timing control registers (CBTCONi, Figures 2.4.4 and

2.4.5)

• Release the internal fault-confinement logic, transmit-, and receive error counters; the module may leave

the error active state depending on the error counts (refer to section 2.4.12).

Ensure to initialize the module by using the above mentioned configuration mode before entering normal

(run) mode; for details refer to section 2.4.5.

Within normal (run) mode the module can be in three different sub-modes, depending on which type of com-

munication functions are actually performed (see Figure 2.4.26):

• Idle: The module’s receive and transmit sections are inactive.

• Receiving: The module is receiving a frame sent by another node.

• Transmitting: The module transmits a frame. Simultaneously, the module may receive its own frame; this is

called auto-receive function, for details refer to section 2.4.8, (5).

From CPU side, the sub-modes may be monitored by the receive- and transmit status bits CREC.1 (Figure

2.4.16) and CTRM.7 (Figure 2.4.3).

Fig. 2.4.26 Transitions among module sub-modes

(3) Sleep mode

This mode enables reduced power consumption by stopping the clock of the module; consequently all func-

tions (incl. communication) are suspended.

Setting the sleep control bit CTRM.1 (Figure 2.4.3) switches the module to sleep mode. Upon entering this

mode, the module’s clock supply stops immediately. CAN related registers retain their contents upon entering

sleep mode. Enter or leave sleep mode via configuration mode only (refer to Figure 2.4.25).

Warning: Switching the module from normal (run) mode straight to sleep mode (bypassing configuration

mode) may cause erroneous frames being sent to the bus or a CTX terminal forcing the bus to dominant level

permanently.

Module idle

CTRM.7 = 0

CREC.1 = 0

detect an

SOF

Module receiving

CTRM.7 = 0

CREC.1 = 1

finish

reception

Module transmitting

CTRM.7 = 1

CREC.1 = 0

start a

transmission

finish

transmission

loose arbitration

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