16.4 CAN Channel
16.4.1 Configuration
The CAN channel can be in:
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Enabled mode
In this mode:
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the CAN channel (internal TxCAN and RxCAN) is enabled,
the input clock is enabled.
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Standby mode
In standby mode:
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the transmitter constantly provides a recessive level (on internal TxCAN) and the receiver is disabled,
input clock is enabled,
the registers and pages remain accessible.
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Listening mode
This mode is transparent for the CAN channel:
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enables a hardware loop back, internal TxCAN on internal RxCAN
provides a recessive level on TXCAN output pin
does not disable RXCAN input pin
freezes TEC and REC error counters
Figure 16-6. Listening Mode
Internal
TxCAN
PD5 TXCAN
PD6 RXCAN
Listen
1
0
Internal
RxCAN
16.4.2 Bit Timing
FSM’s (finite state machine) of the CAN channel need to be synchronous to the time quantum. So, the input clock for bit
timing is the clock used into CAN channel FSM’s.
Field and segment abbreviations:
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BRP: Baud rate prescaler.
TQ: Time quantum (output of baud rate prescaler).
SYNS: Synchronization segment is 1 TQ long.
PRS: Propagation time segment is programmable to be 1, 2, ..., 8 TQ long.
PHS1: Phase segment 1 is programmable to be 1, 2, ..., 8 TQ long.
PHS2: Phase segment 2 is programmable to be ≤ PHS1 and ≥ INFORMATION PROCESSING TIME.
INFORMATION PROCESSING TIME is 2 TQ.
SJW: (Re) Synchronization jump width is programmable between 1 and min(4, PHS1).
The total number of TQ in a bit time has to be programmed at least from 8 to 25.
ATmega16/32/64/M1/C1 [DATASHEET]
147
7647O–AVR–01/15
MICROCHIP [ MICROCHIP ]
