EFD ULTIMUS V User Manual page 36

APPENDIX B
RS-232
Connection
Protocol
1.4 Command Packet Format
Each command packet will contain the following information and will be formatted as
shown below:
[STX] [No. of Byte] [Command] [Data] [Checksum] [ETX]
The following is an example of a command packet. This example uses the Pressure Set
Command ('PS') to send a 50.0psi value to the Ultimus V.
The command:
STX + 08 + PS + 0500 + FO + ETX
The ASCII Codes:
0x02h (STX) + 0x30h ('0') + 0x38h ('8') + 0x50h ('P') + 0x53h ('S') + 0x20h ('') + 0x20h ('' ) +
0x30h ('0') + 0x35h ('5') + 0x30h ('0') + 0x30h ('0') + 0x46h ('F') + 0x30h ('O') + 0x03h (ETX)
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1.4.1 STX
Every command packet will begin with the Start of Packet (0x02h) ASCII character.
1.4.2 No. of Bytes
The number of bytes part of the command packet is the sum of the characters in the
Command and Data parts of the command packet. This value is expressed as a 2-digit
hexadecimal from 0x04h to 0xFFh. The hexadecimal value is encoded as ASCII characters.
1.4.3 Command
The Command part of the Command Packet is next. The list of available commands is
listed in the next section. The command part is four characters long. If the command does
not contain four characters, the remaining characters should be the ASCII space character
(0x20h). The command is transmitted in ASCII characters.
1.4.4 Data
The Data part follows the Command. The Data can be from 0(0x00h) to 251(0xFB)
characters long. This length is dependent on the command. The Data is transmitted in
ASCII characters.
1.4.5 Checksum
The checksum is the next part of the command packet. The checksum is a form of error
checking the command packet. The check sum is calculated by subtracting the ASCII
values of the No. of Bytes, Command and Data from zero (0x00h). Any borrowing is
ignored. The resulting value is transmitted as a 2-digit hexadecimal value encoded in
ASCII.
1.4.6 ETX
The final part of the command packet is the End of Packet (0x03h) ASCII character.
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