User Manual

Chapter 8

Host Commands Using the RS-485 Interface

8–14

You can obtain diagnostic data on the communications link (RS-485

Local-Area Network) using the diagnostic commands. The diagnostic

command has the following structure:

LINK DIAGNOSTIC COMMAND

00000000

00000110

TRANSACTION WORD

HI Byte LOW Byte

FUNCTION CODE

DIAGNOSTIC LOOP DATA

(Only With Diagnostic Loop Command)

Link Diagnostic Command Structure

The following are descriptions of each byte in the diagnostic link command:

COMMAND (Byte 0) - The command byte for the link diagnostics

command has the following structure:

00000110

MSB LSB

0110 = Link

Diagnostics

Command

Bit #6 Cleared

For Command

Always Set to 0

STATUS (Byte 1)- The status byte is cleared for command.

TRANSACTION WORD (Bytes 2 &3) - As with the other commands the

transaction word is a two byte code that is returned (exactly as it was sent) in

the decoder’s reply message.

unic

tion

ink

gnostic

Commands