UM10360 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
User manual Rev. 3 — 19 December 2013 377 of 841
NXP Semiconductors
UM10360
Chapter 16: LPC176x/5x CAN1/2
The table of ranges of Extended Identifiers must contain an even number of entries, of the
same form as in the individual Extended Identifier table. Like the Individual Extended
table, the Extended Range must be arranged in ascending numerical order. The first and
second (3rd and 4th …) entries in the table are implicitly paired as an inclusive range of
Extended addresses, such that any received address that falls in the inclusive range is
received (accepted). Software must maintain the table to consist of such word pairs.
There is no facility to receive messages to Extended identifiers using the FullCAN
method.
Five address registers point to the boundaries between the tables in Acceptance Filter
RAM: FullCAN Standard addresses, Standard Individual addresses, Standard address
ranges, Extended Individual addresses, and Extended address ranges. These tables
must be consecutive in memory. The start of each of the latter four tables is implicitly the
end of the preceding table. The end of the Extended range table is given in an End of
Tables register. If the start address of a table equals the start of the next table or the End
Of Tables register, that table is empty.
When the Receive side of a CAN controller has received a complete Identifier, it signals
the Acceptance Filter of this fact. The Acceptance Filter responds to this signal, and reads
the Controller number, the size of the Identifier, and the Identifier itself from the Controller.
It then proceeds to search its RAM to determine whether the message should be received
or ignored.
If FullCAN mode is enabled and the CAN controller signals that the current message
contains a Standard identifier, the Acceptance Filter first searches the table of identifiers
for which reception is to be done in FullCAN mode. Otherwise, or if the AF doesn’t find a
match in the FullCAN table, it searches its individual Identifier table for the size of Identifier
signalled by the CAN controller. If it finds an equal match, the AF signals the CAN
controller to retain the message, and provides it with an ID Index value to store in its
Receive Frame Status register.
If the Acceptance Filter does not find a match in the appropriate individual Identifier table,
it then searches the Identifier Range table for the size of Identifier signalled by the CAN
controller. If the AF finds a match to a range in the table, it similarly signals the CAN
controller to retain the message, and provides it with an ID Index value to store in its
Receive Frame Status register. If the Acceptance Filter does not find a match in either the
individual or Range table for the size of Identifier received, it signals the CAN controller to
discard/ignore the received message.
Fig 60. Entry in either extended identifier table
CONTROLLER # IDENTIFIER
31 29 28
0
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