Amano PIX-3000x Series, Руководство пользователя

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PIX-3000x Options Manual
17
Checksum (BCC)
Each transmission block will have 2 separate checksums associated with
it.
The first checksum is for the Date/Time block. Each Date/Time block will
have its own checksum. The checksum for the Date/Time block will be
calculated from the first byte of the year and go through the last byte of
the seconds.
The second checksum is for the entire transmission block; this includes
the leading 0's, data type, terminal number and all (4) Date/Time blocks.
The checksum is inclusive from the first byte through the last byte of the
4th Date/Time block. The checksum is a cyclic redundancy check formed
by using exclusive OR logic to combine all elements in the transmission
block.
BCC = data1^data2^data3^...^datan
Error Detection
The transmission format is sent in such a way that makes it possible to
receive the correct time and date even when an error appears in the
transmission. Error detection is accomplished by using the two types of
checksums that are included in the transmission block. If an error is
detected by using the final checksum (located at the end of the
transmission block), the PIX checks each Date/Time block to determine
the correct one. Determining the correct block is done by comparing the
checksums of each block until two match. If two checksums are identical,
it is assumed that the blocks of data are correct. One of these blocks is
chosen as the Date/Time information. If the PIX-3000x is unable to set
the Date/Time, an error message will be displayed on the PIX. The only
way to remove this message is to reset the PIX or to retransmit the
Date/Time correctly. This theory relies on the fact that only one or two
blocks of Date/Time data can be corrupted. If three or more blocks are
corrupted, the correct Date/Time cannot be found.
Software Operation
Refer to the PIXCOMW Installation and Configuration Guide for the
configuration and operation of PIXCOMW software.