Calculating the checksum – Rockwell Automation 2098-DSD-xxx Ultra3000 Host Commands for Serial Interface User Manual
Page 167

Publication 2098-RM003A-EN-P October 2001
Using Host Commands
C-3
6. Select the Settings tab
A. Verify that Emulation is set to VT100.
B. Click on the ASCII Setup button and make these selections:
Calculating the Checksum
The checksum value is used to verify that the data transferred
correctly. When the Ultra family drive receives a command, it verifies
that the checksum is correct before acting on the data.
To calculate the checksum value, you must obtain the ASCII value of
each character in the command string. (A decimal to ASCII conversion
table is on page C-8.) For example, the ASCII value for the number 5
is 53. To calculate the checksum value, you must add together all of
the ASCII values for the numbers or letters in the command you want
to send, subtract this value from 256, convert the result to a
hexadecimal number, and then use only the last two digits. It may
seem complicated, but after an exercise or two it will become clear.
Selected (checkmark)
Not Selected (no checkmark)
Echo typed characters locally
Send line ends with line feeds
Append line feeds to incoming line
ends
Force incoming data to 7 bit ASCII
Wrap lines that exceed terminal width