原创 PIC18Fxx8之CAN信息接收过滤器与屏蔽器

1_00A：信息接收过滤器与屏蔽器

信息接收过滤器与屏蔽器用于确定信息缓冲器MAB中的信息是否被装入其中一个接收缓冲器。一旦一条有效的信息被MAB接收，信息的标识符区域将与过滤器值进行比较，如果相匹配，那么信息将被装入相应的接收缓冲器。过滤器屏蔽器用于确定标识符中的哪一位被过滤器检查。表19.2 介绍了标识符中的每一位如何与屏蔽器和过滤器进行比较来确定信息是否应该被装入接收缓冲器。屏蔽位通常是来确定哪一位是用于用于接收过滤器。如果任一屏蔽位配置为0，那么此位将自动接收，而不考虑过滤器位的状态。

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The Message Acceptance Filters and Masks are used to determine if a message in the message assembly buffer should be loaded into either of the receive buffers.  Once a valid message has been received into the MAB, the identifier fields of the message are compared to the filter values. If there is a match, that message will be loaded into the appropriate receive buffer. The filter masks are used to determine which bits in the identifier are examined with the filters. A truth table is shown below in Table 19-2, that indicates how each bit in the identifier is compared to the masks and filters to determine if a message should be loaded into a receive buffer. The mask essentially determines which bits to apply the acceptance filters to. If any mask bit is set to a zero, then that bit will automatically be accepted, regardless of the filter bit.