7630 datasheet(114/238 Pages) RENESAS

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7630 Group User’s Manual

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2.4 Controller Area Network (CAN) module

2.4.4 Operational modes

The module features three operational modes which can be selected by the sleep control bit CTRM.0 and the

reset/configuration control bit CTRM.1 of the CAN transmit/control register (Figure 2.4.3). Mode transitions may be

carried out according to Figure 2.4.25.

Fig. 2.4.25 Transitions among operational modes

(1) Configuration mode

This mode is used to initialize (refer to section 2.4.5) or reset (refer to section 2.4.6) the module.

Entering the configuration mode initiates the following functions by the module:

• Suspend communication functions

• Set P31/CTX output to recessive (if P31 is configured as CTX output port; see CTRM.2 in Figure 2.4.3)

• Unlock the following configuration register to enable initialization: (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)

• Set module to error active state and clear the internal error counters (refer to section 2.4.12)

• Clear transmit request, transmit buffer control and transmit status bits of CTRM (Figure 2.4.3)

• Clear receive buffer control and receive status bits of CREC (Figure 2.4.16)

• Clear transmit abort bit of CABORT (Figure 2.4.17)

The values of the remaining bits of CTRM, CREC and of other CAN module related configuration registers

(PCON, CBTCON1, CBTCON2, CAC0 to CAC4, CAM0 to CAM4) retain the values they had before entering

the configuration mode.

The contents of the transmit and receive buffer registers CTBi/CRBi (Figures 2.4.19 to 2.4.24) are undefined

in configuration mode.

The module is set to configuration mode upon MCU reset.

Note: Switching the module from normal (run) to configuration mode during an ongoing transmission sus-

pends communication immediately; this causes a corrupted frame on the bus. To avoid the corrupt frame,

either await the successful transmission (see section 2.4.9) or issue an abort transmission request (see sec-

tion 2.4.10) before attempting the mode transition.

(2) Normal (run) mode

Entering this mode initiates the following functions by the module:

• Release communication functions; the module becomes an active node on the network and may transmit

and receive CAN frames. For details on the transmit and receive operations as well as corresponding inter-

rupt functions see sections 2.4.8 to 2.4.11.

Configuration mode

CTRM.1 = 1

CTRM.0 = 0

Normal (run) mode

CTRM.1 = 0, CTRM.0 = 0

Sleep mode

CTRM.1 = 1

CTRM.0 = 1

Reset

idle

receiving

CTRM

.1 =0

CTR

M.1 =1

CTRM.

CTR

M.0 =

transmitting

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