Siemens SIMATIC Distributed I/O System DP/ASi Link Manual page 124

Parameterization Message
C.3 Optimizing Address Assignment
Purpose
For you to be able to address the ASi slaves, you have to allocate the address
assignment within the SIMATIC to every ASi slave.
To make proper use of the limited address space on the SIMATIC, you must
optimize the address assignment of the different slaves.
Method
Optimize the input address area first and then the output address area.
Optimization It has proved sensible to create an address space template for each of the in
puts and each of the outputs. Up to 16 bytes of address space can be assigned
to every address space template. Fig. C-1 shows an example of an address
space template.
Rule
Please observe the following rules, which have proved to be sensible, when
you are tackling address assignment:
C-8
Sort the ASi slaves used according to their address requirement.
Start in byte 0 at bit 0 with an ASi slave having 4 inputs or outputs (data
bits).
Insert all the ASi slaves with 4 data bits first. Then insert all the ASi
slaves with 3 data bits, then 2 data bits and, finally, all ASi slaves having
a single data bit.
In assigning addresses, you must not go beyond byte limits with an ASi
slave. Note that the data must be byte-consistent.
Always try to fill a data byte completely.
Distributed I/O System DP/ASi Link
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