AccuEnergy AcuDC 210 Series, Руководство пользователя

Страница: 64 / 85

54
AcuDC 210/220 Series
used for generating the CRC. Start and stop bits, and the parity bit, do not apply
to the CRC. When generating the CRC, each 8-bit character is exclusive ORed with
the register contents. The result is shifted towards the least significant bit (LSB),
with a zero filled into the most significant bit (MSB) position. The LSB is extracted
and examined, if the LSB equals to 1, the register is exclusive ORed with a preset,
fixed value; if the LSB equals to 0, no action will be taken. This process is repeated
until eight shifts have been performed. After the last (eighth) shift, the next 8-bit
byte is exclusive ORed with the register's current value, and the process repeats for
eight more shifts as described above. The final contents of the register, after all the
bytes of the message have been applied,the final contents of the register, which
should exchange the high-byte and the low-byte, is the CRC value. When the CRC
is appended to the message, the low-order byte is appended first, followed by the
high-order byte.
4.2 Communication Format
All examples shown in this chapter follow the same format of Table 4.3. (All data is
express in Hex)