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Philips Semiconductors
ARM-based Microcontroller
31
29
15
13
Dis
Controller #
able
Figure 34: Entry in fullCAN and Individual Standard Identifier Tables
The table of Standard Identifier Ranges contains paired upper and lower (inclusive) bounds, one pair per word. These must also
be arranged in ascending numerical order.
31
29
26
dis
not
Controller #
able
used
The disable bits in Standard entries provide a means to turn response, to particular CAN Identifiers or ranges of Identifiers, on
and off dynamically. When the Acceptance Filter function is enabled, only the disable bits in Acceptance Filter RAM can be
changed by software. Response to a range of Standard addresses can be enabled by writing 32 zero bits to its word in RAM,
and turned off by writing 32 one bits (0xFFFF FFFF) to its word in RAM. Only the disable bits are actually changed. Disabled
entries must maintain the ascending sequence of Identifiers.
If Extended (29-bit) Identifiers are used in the application, at least one of the other two tables in Acceptance Filter RAM must not
be empty, one for individual Extended Identifiers and one for ranges of Extended Identifiers. The table of individual Extended
Identifiers must be arranged in ascending numerical order.
31
29
28
Controller #
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
CAN Controllers and Acceptance Filter
26
10
not
used
Lower Identifier Bound
Figure 35: Entry in Standard Identifier Range Table
Figure 36: Entry in either Extended Identifier Table
Identifier
16
10
dis
not
Controller #
able
used
Identifier
172
Preliminary User Manual
LPC2119/2129/2292/2294
Upper Identifier Bound
January 08, 2004
16
0
0
0
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