243
7679H–CAN–08/08
AT90CAN32/64/128
5. Tsjw = (1 to 4) x Tscl = (SJW[1..0]+ 1) x Tscl
Notes: 1. The total number of Tscl (Time Quanta) in a bit time must be from 8 to 25.
2. PHS2[2..0] 2 is programmable to be
≤ PHS1[2..0] and ≥ 1.
19.4.4 Fault Confinement
(c.f. Section 19.7 ”Error Management” on page 248).
19.4.5 Overload Frame
An overload frame is sent by setting an overload request (OVRQ). After the next reception, the
CAN channel sends an overload frame in accordance with the CAN specification. A status or
flag is set (OVRG) as long as the overload frame is sent.
Figure 19-9. Overload Frame
19.5 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
19.5.1 Number of MObs
This device has 15 MObs, they are numbered from 0 up to 14 (i=14, no MOb 15).
Ident "A" Cmd Message Data "A" CRC InterframeA Ident "B"
Overload Frame
Overload Frame
RXCAN
Setting OVRQ bit
OVRG bit
Resetting OVRQ bit
TXCAN
OVRQ bit
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