AT90CAN128-16AE ATMEL Corporation, AT90CAN128-16AE Datasheet - Page 237

• Manufacturer Part Number: AT90CAN128-16AE
• Description: 8-bit Avr Microcontroller With 128K Bytes of Isp Flash And CAN Controller.flash (Kbytes) 128 Vcc (V) 2.7-5.5 EEPROM (Kbytes) 4 SRAM (bytes) 4K CAN (mess. Obj.) 15
• Manufacturer: ATMEL Corporation

Overload Frame
Message Objects
Operating Modes
Disabled
Tx Data & Remote Frame
4250C–CAN–03/04
An overload frame is sent by setting an overload request (OVRQ). After the next recep-
tion, the CAN channel sends an overload frame in accordance with the CAN
specification. A status or flag is set (OVRF) as long as the overload frame is sent.
Figure 116. Overload Frame
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 numbered from 0 up to 14 (no MOb [15]). They are independent but pri-
ority is given to the lower one in case of multi matching. The operating modes are:
Every MOb has its own fields to control the operating mode. There is no default mode
after RESET. Before enabling the CAN peripheral, each MOb must be configured (ex:
disabled mode - CONMOB=00).
Table 95. MOb Configuration
In this mode, the MOb is “free”.
1. Several fields must be initialized before sending:
Instructions
–
–
–
–
–
–
OVRQ bit
OVFG bit
RXCAN
TXCAN
Disabled mode
Transmit mode
Receive mode
Automatic reply
Frame buffer receive mode
Identifier tag (IDT)
MOb Configuration
0
0
1
1
0
1
0
1
Ident "A"
Cmd
Reply Valid
Setting OVRQ bit
Message Data "A"
x
x
x
0
1
x
RTR tag
CRC
x
0
1
0
1
x
A
Interframe
Resetting OVRQ bit
Disabled
Tx Data Frame
Tx Remote Frame
Rx Data Frame
Rx Remote Frame
Rx Remote Frame then,
Tx Data Frame (reply)
Frame Buffer Receive mode
Overload Frame
Overload Frame
Operating Mode
AT90CAN128
Ident "B"
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