Rainbow-electronics ATmega64M1 Manuel d'utilisateur télécharger pdf (Page 174)

174

8209A–AVR–08/09

ATmega16M1/32M1/64M1

20.6 Message Objects

The MOb is a CAN frame descriptor. It contains all information to handle a CAN frame. This

means that a MOb has been outlined to allow to describe a CAN message like an object. The set

of MObs is the front end part of the “mailbox” where the messages to send and/or to receive are

pre-defined as well as possible to decrease the work load of the software.

The MObs are independent but priority is given to the lower one in case of multi matching. The

operating modes are:

– Disabled mode

– Transmit mode

– Receive mode

– Automatic reply

– Frame buffer receive mode

20.6.1 Number of MObs

This device has 6 MObs, they are numbered from 0 up to 5 (i=5).

20.6.2 Operating Modes

There is no default mode after RESET.

Every MOb has its own fields to control the operating mode. Before enabling the CAN periph-

eral, each MOb must be configured (ex: disabled mode - CONMOB=00).

20.6.2.1 Disabled

In this mode, the MOb is “free”.

20.6.2.2 Tx Data & Remote Frame

1. Several fields must be initialized before sending:

– Identifier tag (IDT)

– Identifier extension (IDE)

– Remote transmission request (RTRTAG)

– Data length code (DLC)

– Reserved bit(s) tag (RBnTAG)

– Data bytes of message (MSG)

Table 20-1. MOb Configuration

MOb Configuration Reply Valid RTR Tag Operating Mode

00 x xDisabled

x 0 Tx Data Frame

x 1 Tx Remote Frame

x 0 Rx Data Frame

Rx Remote Frame

1 Rx Remote Frame then, Tx Data Frame (reply)

1 1 x x Frame Buffer Receive Mode

1 2 ... 169 170 171 172 173 174 175 176 177 178 179 ... 342 343

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Rainbow-electronics ATmega64M1 Manuel d'utilisateur Page 174