redundancy time for s7400h-s7400r

Dear Sir,

What is the differance between S7-400R and S7-400H System?
what is the redundancy time for S7-400R and S7-400H ?

regards........

S7-R or software redundancy as it is officially called, is using standard CPUs of S7 300/400 family and then adding special user program that you get from Siemens to acheive redundancy.It is also called warm stand-by. This is a main point that redundancy is partof user program and is dependanton theuser program toget redundancy. Programming mistakes from user can affect the redundancy performance too.This is is not ideal for fast processes and critical applications where switch over time has to be really small. The communication between the processors can be on MPI, Profibus or Ethernet. Everything is depended on the user programs and there are certain guidelines in you program that you have to follow to achieve redundancy. The changeover time beween the CPUs can be noticable and could take few seconds.

https://www.automation.siemens.com/simatic/controller/html_76/produkte/software-redundancy.htm

S7-400H or hotstand-by (also known as fault tolerance) is available only in S7-400 family and has specially designedprocessors for it. Redundancy is part of the firmware and no addition in user program is required for achieving redundancy. You can take a program running onstandard system and change the hardware config to400-H and it is ready to beused in redundancy in most cases.The communication between the CPUsis over a dedcicated fiber cablesvia synchmodules on the CPU. The CPUs run in synchronization and the scan the program together to make sure both the CPUs have the same state of all memeory areas at any given time. This ensures a bumpless transfer and is suitable for application that require high availability process and require less than 100ms changeover time.

https://www.automation.siemens.com/simatic/controller/html_76/produkte/simatic-s7-400-h.htm