If the length Modbus TCP/IP Data is limited to 259 bytes (250 for Modbus serial), what is the length for a Siemens H1 message and Allen-Bradley EtherNet/IP message?

Thinking about the perfomance and speed needed by any SCADA software to read 5000 DI (2 bits) and 2500 AI (16 bits) by using Ethernet as communication wiring, I wonder how fast could be read all this data using Siemens H1 protocol or Allen-Bradley EtherNet/IP instead of Mobdus TCP/IP?

Let's assume that we could read 3 messages simultaneously/parallel (because of it's TCP/IP) without affecting PLC scan (sure we could read more than 3 but it's just a number!)

If I use Modbus TCP/IP, my numbers are:
a) To read 5000 DI:
- 1000 I/Os per message (250*8/2)
- 3000 I/Os per SCADA's poll set (1000*3)
=> 2 times to read these 5000 DI (5000/3000= 1,666).. or 6 polls (individually) from SCADA.

b) To read 2500 AI:
- 125 I/Os per message (250*8/16)
- 375 I/Os per SCADA's poll set (125*3)
=> 7 times to read these 2500 DI (2500/375= 6,666).. or 21 polls from SCADA.

What would these numbers be if we use Siemens H1 or Allen-Bradley EtherNet/IP??.

Thanks in avance for any comments.

Saludos.
Gustavo A. Valero P.

 

Some time ago, some guy from Siemens told me that H1 protocol uses a frame of 1600 bytes but I could never verify it.

 

The TCP's data field can be from 46 to 1500 bytes, therefore, H1 should use these 1500 bytes and be faster than Modbus TCP/IP. I hope some guy from Siemens can assure it.

Regards