MikroElektronika PIC Microcontrollers PIC18 Instrukcja Użytkownika Pobierz pdf (Strona 11)

9.1.6 ACK Field

The ACK field indicates that the frame has been received normally. This field

consists of 2 bits, one for ACK slot and one for ACK delimiter.

9.2 Remote Frame

The remote frame is used by the receiving unit to request transmission of a

message from the transmitting unit. It consists of six fields (see Figure 9.10): start

of frame, arbitration field, control field, CRC field, ACK field, and end of

frame field. A remote frame is the same as a data frame except that it lacks a

data field.

9.3 Error Frame

Error frames are generated and transmitted by the CAN hardware and are used to

indicate when an error has occurred during transmission. An error frame consists of

an error flag and an error delimiter. There are two types of error flags: active, which

consists of 6 dominant bits, and passive, which consists of 6 recessive bits. The

error delimiter consists of 8 recessive bits.

9.4 Overload Frame

The overload frame is used by the receiving unit to indicate that it is not yet

ready to receive frames. This frame consists of an overload flag and an overload

delimiter. The overload flag consists of 6 dominant bits and has the same

structure as the active error flag of the error frame. The overload delimiter

consists of 8 recessive bits and has the same structure as the error delimiter of

the error frame.

SOF

Arbitration

field

Control field

ACK

CRC

EOF

Figure 9.10: Remote frame

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MikroElektronika PIC Microcontrollers PIC18 Instrukcja Użytkownika Strona 11