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PPI / MPI - What are the real differences?

Created by: Floyd at: 1/4/2008 11:40 PM (9 Replies)

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1/4/2008 11:40 PM	Rate (0)
Floyd Posts: 130 Rating: (1)	For years I have been confused about the exact differences between PPI and MPI. I understand that PPI is Point to Point Interface, and MPI is Multi Point Interface. What i don't understand is why there are different cables for PPI and MPI and how you can have mulitplenodes on a S7-200 PPI network yet its not MPI. I have seen the S7-200 platform grow sustancially over the last 5 years, and its been hard at times to keep up. Can someone please help me understand this? Where have the most difficulty is using PPI with WinccFlexible HMI's (TP170/7 product line) and cabling to program the plc and download to the HMI, w/o unhooking things.
Floyd Posts: 130 Rating: (1)
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1/5/2008 2:01 PM	Rate (0)
Late Platinum Expert Joined: 1/7/2006 Last visit: 11/17/2023 Posts: 2705 Rating: (318)	Dear Floyd, Like you say the PPI is for the S7-200 range developed and the MPI is developed for the S7-300 and the S7-400. So thay have the best features for the S7 where they are developed for. Maybe you could do something with the next FAQ: Which HMI components can you connect with S7-200 CPU and what should you watch out for when doing so?
	I hope that the answer will help, if you have still questions, don't hesitate to ask me. All the best, Late Never say never, think in solutions, not in trouble......
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1/5/2008 6:10 PM	Rate (1)
J_Bell Posts: 5822 Rating: (412)	Dear Floyd, I have to admit I am not the specialist in explaining the deep differences but I do know that the main difference between the MPI and PPI networks are: - MPI is PROFIBUS based and is using the regulations of PROFIBUS too... So you have max. 256 Byte long telegrams with Header and Taylor like PROFIBUS. - PPI is RS485 based and closely to PROFIBUS but due to the smaler performance for Communication the PPI Telegramm can contain gaps within the Data... so you have usually no defined Telegramlength like you would need it for PROFIBUS. Due to this MPI and PPI do not work together. I know this differenceis very rough. But I hope it helps you to understand. Best regards J_Bell
J_Bell Posts: 5822 Rating: (412)
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1/5/2008 6:38 PM	Rate (0)
Navnag Platinum Expert Joined: 11/21/2007 Last visit: 9/25/2024 Posts: 2325 Rating: (308)	Hello Floyd As far as i understand S7-200 was developed by and for SE&A USA to compete with other manufacturer's similar products. and S7-300 and 400 by Siemens AG germany to replace SIMATIC S5, with entirely different target markets and applications. Yoy are right calling PPI as "Point to Point" is basically a misnomer because in PPI network also you can have several PLCs and HMIs. It is correct that PPI is basically a glorified RS485 networking. Basically it is meant for slow speed communication for short data packets. MPI However works on a different principle. It is loosely based on Profibus standard but some additional features like Global data communication etc have been added and DP feature has beenremoved. I guess this waythere is no need to use costly "Profibus" chips. Regards Navnag
	There is no such thing as the last bug in a program There are no stubborn bugs, There are only stubborn Debuggers.
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1/7/2008 4:34 PM	Rate (0)
Floyd Posts: 130 Rating: (1)	Thank you all for the posts. One thing that confuses me these days is this. To link a S7-200 to a TP-177x HMI, you must enable the MPI/DP port. Is the HMI automatically distinguishing the PPI protocol based on the configuration of "Connections"? The same port is used for PPI/MP/DP, how does it know which to use?
Floyd Posts: 130 Rating: (1)
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1/7/2008 11:36 PM	Rate (0)
Late Platinum Expert Joined: 1/7/2006 Last visit: 11/17/2023 Posts: 2705 Rating: (318)	Dear Floyd, All protocols are RS485 based, so that is why it could be done on one port, the other thing is that MPI is a derivate of DP, PPI is a simpler MPI protocol and made for Point-to-Point communication.
	I hope that the answer will help, if you have still questions, don't hesitate to ask me. All the best, Late Never say never, think in solutions, not in trouble......
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1/8/2008 4:41 PM	Rate (0)
Floyd Posts: 130 Rating: (1)	How does the HMI know to use PPI verses MPI, there isn't a PPI mode in the control panel? Does it know from the connections tab? Can it do MPI and PPI on the same port, i.e. talk to a 224XP and a 315dp?
Floyd Posts: 130 Rating: (1)
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10/20/2015 10:08 AM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4766 Rating: (122)	New question published by pratikbhamare is split to a separate thread with the subject S7-200 PLC has profibus port on cpu or not?. Best regards Min_Moderator

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11/4/2015 11:02 AM	Rate (0)
Wit_Moderator Moderator Joined: 8/21/2014 Last visit: 11/12/2024 Posts: 1024 Rating: (14)	New question published by pratikbhamare is split to a separate thread with the subject Converting MPI port to PROFIBUS within software. Best regards The Helping Hand
	My Forum is the place to personalize your profile, track your topics, and maintain content that interests you. Best regards Wit_Moderator
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5/11/2017 1:45 PM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4766 Rating: (122)	New question published by NikosNikol is split to a separate thread with the subject Connect pc with plc with profibus cable and adapter. Best regards Min_Moderator

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