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
0x32 in hex, 48 in
decimal) from Zero (
0x00). The resulting negative value’s least significant byte is the Checksum value.
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 (
A2) text packet.
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 0x03 or CTRL+C), except as
noted below.
NOTE: The End of Text control character (
ETX / 0x03) is not added when sending ENQ (0x05), ACK(0x06),
NAK(0x15), or EOT(0x04), because these are single-byte control characters, not text.
Appendix B — RS‑232 Protocol (continued)
Ultimus V High Precision Fluid Dispenser
44 www.nordsonefd.com info@nordsonefd.com 800-556-3484 Sales and service of Nordson EFD dispensing systems are available worldwide.
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