Checksum; Etx - Nordson EFD Ultimus V Manuel Utilisateur

Doseur de Fluide Haute Précision Ultimus V
Annexe B — Protocole RS-232 (suite)

2.3.5 Checksum

The Checksum is the next part of the text packet. The Checksum is a form of error checking for the text packet. The
Checksum is calculated by subtracting the actual value of each ASCII byte (e.g., "2" in ASCII is
decimal) from Zero (
Each byte (ASCII character) starting with No. Bytes (2.3.2) through Data (2.3.4) is used to calculate the Checksum.
Converting the least significant byte (2 digits in hex) to ASCII characters and appending them to the rest of the text
packet provides the Checksum value. If the Checksum is incorrectly calculated / transmitted with the text packet,
the dispenser responds with a Failure Command (
The Checksum can also be understood as:
Checksum = 0 – (Byte 1 of No. Bytes + Byte 2 of No. Bytes + Command/Data byte[1] +
Command/Data byte[2] + Command/Data byte[3] + ... + Command/Data byte[n])
Where "n" = the number of bytes
An example of the Checksum calculation is shown in 2.3.7.

2.3.6 ETX

The final part of the text packet is the End of Text control character (hexadecimal
noted below.
NOTE: The End of Text control character (
NAK ( 0x15 ), or EOT
44
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0x00 ). The resulting negative value's least significant byte is the Checksum value.
ETX / 0x03
( 0x04 ), because these are single-byte control characters, not text.
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A2 ) text packet.
) is not added when sending
0x32 in hex, 48 in
0x03 or CTRL+C), except as
ENQ ( 0x05 ), ACK ( 0x06 ),