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Theory of 984 HSBY Operation
40
840 USE 106 00 January 2003
Customizing Options
Custom State
RAM Transfer
Area
If you want to set up a custom state RAM transfer area, you can control your
transferred amounts using a Hot Standby configuration extension (refer to
Additional
Guidelines for IEC Hot Standby , p. 147
). The configuration extension provides three
alternatives to the default transfer area:
You can define the number of 0x, 1x, 3x, and 4x reference data types that you
want transferred in each scan.
You can define a certain amount of reference data types to be transferred on
each scan with additional data to be transferred in groups over multiple scans,
beginning with 0x registers and proceeding in turn with 1x, 3x, and 4x registers.
You can transfer all the configured reference data types in your system’s state
RAM on every scan.
These options allow you to design a transfer area that is as small as 16 4x output
registers or large enough to encompass all of your controllers’ state RAM (10K, 32K,
or 64K, depending on the type of Quantum controllers you are using in your Hot
Standby system).
The reference data of each type (0x, 1x, 3x, and 4x) is placed in the state RAM
transfer area, starting at the lowest reference number (000001 for coils, 100001 for
discrete inputs, 300001 for register inputs, and 400001 for register outputs). It is
accumulated contiguously up to the amount of each data type you specify. The total
number of each reference type in the state RAM transfer area must be a multiple of
16.
For example, if you indicate that the number of coils in the transfer area is 96, coils
000001... 000096 are transferred from the Primary to the Standby controller. Any 0x
references beyond 000096 used in state RAM are not transferred.
The additional state RAM data to be sent over multiple scans can also be of any or
all of the four reference data types, and must also be specified in multiples of 16.
The additional reference data region for each data type starts at the lowest available
reference number. For example, if 2048 coils are transferred on every scan
(000001... 002048), and you schedule 1024 additional coils for transfer over multiple
scans, references 002049... 003072 are used for the additional transfer data.
The additional transfer is handled by specifying the number of scans over which you
want to send the additional data. For example, if you specify two scans in which to
transfer coils 002049... 003072, then coils 002049... 002560 are sent with coils
000001... 002048 on one scan and coils 002561... 003072 are transferred with coils
000001... 002048 on the next scan.