DAVIS Vantage Pro - CRC Calculation

Page 32 of 52
Each "Page" is 267 bytes and contains 5 records of data. There are a total of 512 pages of archive
memory for a total of 2560 records. If a "DMPAFT" command results in downloading the entire
archive, 513 pages will be downloaded. The first and last pages in this case are identical.
The format of each page is:
1 Byte sequence number (starts at 0 and wraps from 255 back to 0)
52 Byte Data record
52 Byte Data record
52 Byte Data record
52 Byte Data record
52 Byte Data record
4 Byte unused bytes
2 Byte CRC
See section IX.3 for details on the format of the archive data record.
Example (download records after June 6, 2003 9:30am [270 pages, the first valid record is 2]):
>"DMPAFT"<LF>
<<ACK>
-- Send the Date and Time stamp --
><0xC6><0xCE><0xA2><0x03>
-- Send the calculated CRC 0xE2B4 –
><0xE2><0xB4>
<<ACK>
-- Vantage responds with the number of pages it will send --
<<0x0E><0x01><0x02><0x00><2 Bytes of CRC Data>
-- Begin the download – Use <ESC> instead to cancel it
><ACK>
-- Block sequence number
<<0x00>
<<52 byte data record 0>
<<52 byte data record 1>
-- The next record is the first record with new data
<<52 byte data record 2>
<<52 byte data record 3>
<<52 byte data record 4>
<<4 unused bytes>
<<2 byte CRC>
-- At this point verify the CRC and send either <ACK>, <0x21>, or <ESC>
XI. CRC calculation
The console uses the same CRC calculation that was used by earlier Davis Instruments weather
stations.