Cardinal 748 - Checksum Calculation

12
Serial Command Format - STX8CKsumETX
Hex Format to Transmit - 2H 38H 33H 38H 3H
Equivalent Computer or Terminal Keys to press - Ctrl B 8 3 8 Ctrl C
KeyCommand - 9
Equivalent Keyboard Key - none
Function - Perform Push Button Tare function. This will set the
GROSS weight as the TARE value and switch to
the NET mode. NOTE: The setup parameter,
PbtAr has no effect on this function
Serial Command Format - STX9CKsumETX
Hex Format to Transmit - 2H 39H 33H 39H 3H
Equivalent Computer or Terminal Keys to press - Ctrl B 9 3 9 Ctrl C
1
The xH xH xH xH xH xH and yH yH yH yH yH yH are the HEX equivalent of each character in
the weight value. For example, if the weight value is 1234.1, the HEX equivalent is 31H 32H 33H
34H 2EH 31H.
2
The zzH is the HEX equivalent of the ChecKsum value. NOTE: For instructions on how to
calculate the checksum value, refer to the CHECKSUM CALCULATION section of this manual.
3
Refer to an ASCII character code table of your computer or terminal for the corresponding
key(s) to press for the HEX ChecKsum value.
RESPONSES TO SERIAL COMMAND FUNCTIONS
The 748 will respond to every serial command received. The format will serve to indicate the manner
in which the serial command was processed. The general format for the response to a serial
command is:
Response [RejectCode]
where: Response - ACK if the command was processed
NAK if the command was not processed
RejectCode - If NAK was transmitted to show that the command was not
processed, a code number will be transmitted to indicate the
reason for rejection of the command
0 - Unable to process command (i.e. Print command sent while
weight was unstable)
1 - Invalid Cksum (i.e. checksum incorrectly calculated)
2 - Invalid Character Count (i.e. data length wrong, weight value
exceeds scale capacity or wrong division value, etc.)
3 - Invalid Decimal Point position (i.e. decimal point missing or in
wrong location)
4 - Invalid Command (i.e. improper command format or invalid
KeyCommand)
5 - Invalid Sub-Command (i.e. invalid tare weight, preset number,
or preset weight, Bar graph start or stop weight)
CHECKSUM CALCULATION
The checksum (Cksum) for KeyCommands with SubCommands or weight values to be entered (5,
6, and 7) are calculated by XORing each byte of the command,
excluding the STX and ETX
characters. The CKsum is then entered as a two (2) byte ASCII representation of the calculated
HEX value. For example:
TARE command (5): STX5xxxxxxCKsumETX (xxxxxx = tare weight value)
Tare Weight Value = 1234
CKsum =
1F (35h, XOR 31h XOR 32h XOR 33h XOR 34h XOR 2eh)
String to send, 02h 35h 31h 32h 33h 34h 2eh
31h 3fh 03h