The syntax of the "C" command is:
CRC string
where there is a space between "CRC" and the string
string is simply a NULL-terminated character string
Notes:
No distinction is made between uppercase and lowercase.
The first BYTE (i.e., character) after "CRC" is omitted from the calculation.
The terminating NULL is included in the calculation.
The CRC (Cylic Redundancy Check) is a way of detecting an error in block of
data. It calculates a numeric value over the data block which can be used
for comparison later to see if anything changed. This command begins by
skipping the first byte after "CRC", whether it is a space or any other
character. The NULL string terminator is included in the calculation.
This is present in the Operating System Commands because a 16-bit CRC
calculation was needed for data transmission, the "C" command was not being
used for something else, and it was found to have occasional other uses.
>CRC 1
The CRC over "1" (2 bytes) is 0x2014
>CRC 12
The CRC over "12" (3 bytes) is 0x6F35
>CRC 123
The CRC over "123" (4 bytes) is 0xE7BB
>CRCx123
The CRC over "123" (4 bytes) is 0xE7BB
>CRC Longer test string
The CRC over "Longer test string" (19 bytes) is 0xA75F
>
The most FLASH codespace was used by the output strings. This command is a
good candidate for a Command Extension
replacement.
See also:
The CRC
and RunningCRC system subroutines and
CRC-16 (or CRC-16-IBM.)