
49.5.9.1 CAN FD ISO compliance
The CAN FD protocol has been improved to increase the failure detection capability that
was in the original CAN FD protocol, which is also called non-ISO CAN FD, by CAN in
Automation (CiA). A three-bit stuff counter and a parity bit have been introduced in the
improved CAN FD protocol, now called ISO CAN FD. The CRC calculation has also
been modified. All these improvements make the ISO CAN FD protocol incompatible
with the non-FD CAN FD protocol. The non-ISO CAN FD is still supported by FlexCAN
so that it can be used mainly during an intermediate phase, for evaluation and
development purposes.
Therefore, it is strongly recommended to configure FlexCAN to the ISO CAN FD
protocol by setting the ISOCANFDEN field in the CTRL2 register.
49.5.9.2 CAN FD frames
The ISO 11898-1 standard specifies the Classical Frame format compliant to ISO
11898-1 (2003) and introduces the CAN Flexible Data Rate Frame format. The Classical
Frame format allows bit rates up to 1 Mbit/s and payloads up to 8 bytes per frame. The
Flexible Data Rate Frame format allows bit rates higher than 1 Mbit/s and payloads
longer than 8 bytes per frame. FlexCAN can receive and transmit CAN FD messages
interleaved with Classical CAN messages.
There are three additional control bits in the CAN FD frame. The Extended Data Length
(EDL) bit enables a longer data payload with different data length coding. The Bit Rate
Switch (BRS) bit decides whether the bit rate is switched inside a CAN FD format frame.
The Error State Indicator (ESI) flag is transmitted dominant by error active nodes, and
recessive by error passive nodes. There are no Remote Frames (see
the CAN FD format. A message configured to transmit a Remote Frame is always sent
out in the Classical CAN format. When an FD frame is received and matches a mailbox,
the RTR bit in the receiving message buffer is negated. The RTR bit must be considered
in classical frames only.
CAN FD messages may be formatted as long frames where the data field exceeds 8 bytes,
and may range from 12 up to 64 bytes. They can also be configured to support bit rate
switching, where the control field, the data field, and the CRC field of a CAN frame are
transmitted with a higher bit rate than the beginning and the end of the frame. Messages
in Classical CAN format are limited to transport a maximum payload of 8 bytes at
nominal rate. The following figure illustrates the message formats for Classical and FD
frames with either standard or extended ID.
Functional description
MWCT101xS Series Reference Manual, Rev. 3, 07/2019
1682
NXP Semiconductors
Содержание MWCT101 S Series
Страница 2: ...MWCT101xS Series Reference Manual Rev 3 07 2019 2 NXP Semiconductors...
Страница 42: ...MWCT101xS Series Reference Manual Rev 3 07 2019 42 NXP Semiconductors...
Страница 50: ...Conventions MWCT101xS Series Reference Manual Rev 3 07 2019 50 NXP Semiconductors...
Страница 70: ...Aliased bit band regions MWCT101xS Series Reference Manual Rev 3 07 2019 70 NXP Semiconductors...
Страница 78: ...Pinout diagrams MWCT101xS Series Reference Manual Rev 3 07 2019 78 NXP Semiconductors...
Страница 96: ...WCT101xS safety concept MWCT101xS Series Reference Manual Rev 3 07 2019 96 NXP Semiconductors...
Страница 130: ...Functional description MWCT101xS Series Reference Manual Rev 3 07 2019 130 NXP Semiconductors...
Страница 200: ...Initialization application information MWCT101xS Series Reference Manual Rev 3 07 2019 200 NXP Semiconductors...
Страница 284: ...Functional description MWCT101xS Series Reference Manual Rev 3 07 2019 284 NXP Semiconductors...
Страница 430: ...Functional Description MWCT101xS Series Reference Manual Rev 3 07 2019 430 NXP Semiconductors...
Страница 472: ...Application Information MWCT101xS Series Reference Manual Rev 3 07 2019 472 NXP Semiconductors...
Страница 508: ...Reset memory map and register descriptions MWCT101xS Series Reference Manual Rev 3 07 2019 508 NXP Semiconductors...
Страница 528: ...Module clocks MWCT101xS Series Reference Manual Rev 3 07 2019 528 NXP Semiconductors...
Страница 634: ...SRAM configuration MWCT101xS Series Reference Manual Rev 3 07 2019 634 NXP Semiconductors...
Страница 696: ...Initialization and application information MWCT101xS Series Reference Manual Rev 3 07 2019 696 NXP Semiconductors...
Страница 818: ...Functional description MWCT101xS Series Reference Manual Rev 3 07 2019 818 NXP Semiconductors...
Страница 960: ...Functional description MWCT101xS Series Reference Manual Rev 3 07 2019 960 NXP Semiconductors...
Страница 970: ...Memory Map and Register Definition MWCT101xS Series Reference Manual Rev 3 07 2019 970 NXP Semiconductors...
Страница 992: ...ADC calibration scheme MWCT101xS Series Reference Manual Rev 3 07 2019 992 NXP Semiconductors...
Страница 1118: ...Application information MWCT101xS Series Reference Manual Rev 3 07 2019 1118 NXP Semiconductors...
Страница 1294: ...Initialization Procedure MWCT101xS Series Reference Manual Rev 3 07 2019 1294 NXP Semiconductors...
Страница 1348: ...Functional description MWCT101xS Series Reference Manual Rev 3 07 2019 1348 NXP Semiconductors...
Страница 1366: ...Functional description MWCT101xS Series Reference Manual Rev 3 07 2019 1366 NXP Semiconductors...
Страница 1514: ...Functional description MWCT101xS Series Reference Manual Rev 3 07 2019 1514 NXP Semiconductors...
Страница 1726: ...Debug and security MWCT101xS Series Reference Manual Rev 3 07 2019 1726 NXP Semiconductors...
Страница 1740: ...Initialization application information MWCT101xS Series Reference Manual Rev 3 07 2019 1740 NXP Semiconductors...
Страница 1760: ...MWCT101xS Series Reference Manual Rev 3 07 2019 1760 NXP Semiconductors...