B&B Electronics I-7060 - Quick Start Guide - Manual (Page 52)

Getting Started for I-7000 Series Modules
Date: Jan-08, 2002 Version 1.02 page: 52
6 FAQ
6.1 7000 FAQ
Q: How to compute the checksum?
A:
The steps to compute the checksum are given as follows:
Step 1: Checksum=0;
Step 2: Sums all "Command byte" with index conduct this loop:
Checksum = Checksum + Command byte [index]
Step 3: Checksum = Checksum & 0xff
Step 4: Convert Checksum to ASCII high byte and ASCII low byte
For example,
Command = $012[Enter]
Checksum = '$'+'0'+'1'+'2' = 0x24+0x30+0x31+0x32 = 0xB7
Checksum & 0xff = 0xB7
Checksum high byte = 'B'
Checksum low byte = '7'
Command with checksum = $012B7[Enter]
Q: When to use a repeater in the RS-485 network?
A:
Users should use a repeater if the network has more than 256 modules,
or if it is being sent farther than 1.2 km.