CET-5 DeviceNet Explicit Messaging

Greetings,

I'm trying to retrieve some parameters from a Sprecher & Schuh CET-5 Motor Protection Relay by explicit messaging on a ControlLogix 1756 series PLC, however I am having issues decoding the addressing (class, attribute, instance) from the EDS file.

The EDS file entries for the parameters are as follows:

Param354 =
0,
8,"21 0F 00 25 62 01 30 01",
0x10,199,2,
"AVERAGE CURRENT ","A ",
"",
0,65535,0,
1,1,1,0,
0,0,0,0,0;

Param396 =
0,
8,"21 0F 00 25 8C 01 30 01",
0x14,199,2,
"THERM CAP USED ","% ",
"",
0,9990,0,
1,10,1,0,
0,0,0,0,1;

Param444 =
0,
8,"21 0F 00 25 BC 01 30 01",
0x12,210,2,
"TRIP STATUS LO "," ",
"",
0,65535,0,
1,1,1,0,
0,0,0,0,0;

Out of all these, the only address byte that changes is the 5th from the left. I can only assume this is the attribute, however I have no idea what to set as class and instance.

Is anyone able to help me out?

Many thanks,
John

The class, instance, and attribute values are normally

20 xx
24 xx
30 xx

These point to single-byte values.

When there are extended (i.e. >256) possibilities then you can get...

class 21 XX XX
inst 25 XX XX
attr 31 XX XX

You can get mixtures of these...

20 XX
25 XX XX
30 XX

Or,

21 XX XX
24 XX
31 XX XX

When adding double-byte numbers to your ControlLogix MSG configuration, enter the two bytes in reverse order. You can enter them as HEX, and RSLogix5000 sorts it out for you, saves you having to do the hex to decimal conversion.

21 0F 00
25 62 01
30 01

Class enter 16#000F
Inst enter 16#0162
Attr enter 16#01

Ive edited my post a couple of times, trying to make it easier to understand - read it again, and anything you're unsure of, post back...

I suspect (but not sure)

Class....
20, 1 byte value
21, 2 byte value
22, 3 byte value
23, 4 byte value

Instance.....
24, 1 byte value
25, 2 byte value
26, 3 byte value
27, 4 byte value
28, 5 byte value
29, 6 byte value

Attribute....
30, 1 byte value
31, 2 byte value
32, 3 byte value
33, 4 byte value

I've put bold on the one's I know to be valid, just guessing on the rest without trawling through the CIP specs

That's brilliant Daba. Thankyou very much.

I have downloaded the code and it is working perfectly.