Rainbow-electronics ATmega64M1 Manual de usuario descargar pdf (Pagina 171)

171

8209A–AVR–08/09

ATmega16M1/32M1/64M1

20.5 CAN Channel

20.5.1 Configuration

The CAN channel can be in:

• Enabled mode

In this mode:

– the CAN channel (internal TxCAN & RxCAN) is enabled,

– the input clock is enabled.

• Standby mode

In standby mode:

– 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.

• Listening mode

This mode is transparent for the CAN channel:

– 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 20-6. Listening Mode

20.5.2 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:

• 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).

PD5

TXCAN

PD6

RXCAN

internal

TxCAN

internal

RxCAN

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