Mask Function - NEC UPD703116 User Manual

32-bit single-chip microcontrollers

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11.6 Mask Function

A mask linkage function can be defined for each received message.

This means that there is no need to distinguish between local masks and global masks.

When the mask function is used, the received message's identifier is compared with the message buffer's identifier

and the message can be stored in the defined message buffer regardless of whether the mask sets "0" or "1" as a

result of the comparison.

When the mask function is operating, a bit whose value is defined as "1" by masking is not subject to the

abovementioned comparison between the received message's identifier and the message buffer's identifier.

However, this comparison is performed for any bit whose value is defined as "0" by masking.

For example, let us assume that all messages that have a standard-format ID in which bits ID27 to ID25 = 0 and

bits ID24 and ID22 = 1 are to be stored in message buffer 14 (which is linked by mask 1 as explained in 11.10 (7)).

The procedure for this example is shown below.

<1> Identifier bits to be stored in message buffer

Remark x = don't care

Messages with an ID in which bits ID27 to ID25 = 0 and bits ID24 and ID22 = 1 are registered (initialized) in

message buffer 14 (see 11.10 (6)).

<2> Identifier bits set to message buffer 14 (example)

(Using CAN message ID registers L14 and H14 (M_IDL14 and M_IDH14))

Message buffer 14 is set as a standard-format identifier linked to mask 1 (see 11.10 (7)).

CHAPTER 11 FCAN CONTROLLER

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