PMS request: READ
(Original Document)
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At a Glance
This request is used to read variables from a device connected to the INTERBUS bus.
This request is carried out using the READ_VAR communication function.
Syntax
The syntax of the communication function is presented in the following format:
READ_VAR(ADDR('r.m.0.pcp'),'PMS', index, subindex, %MWk:4, %MWi:L)
The following table describes the various parameters of the function.
Parameter
Description
ADDR('r.m.0.pcp')
Address of the destination entity of the exchange:
  • r.m: rack, module,
  • 0 : channel (always 0),
  • pcp: pcp channel number.
'PMS'
Type of PMS object (always PMS in upper case).
index
Double word or value identifying the object to be accessed.
subindex
Word or value specifying the object to be accessed.
%MWk:4
Exchange management parameters: four words identifying the address of the Control Expert data used to control the READ_VAR function.
%MWi:L
Word table containing the value of read objects (minimum length = 1).
Management parameters
The following table gives details of %MWk:4 words.
Word number
Most significant byte
Least significant byte
Data managed by
%MWk
Exchange number
Activity bit
system
%MWk+1
Operation report
Communication report
%MWk+2
Timeout: value complies with the bandwidth of INTERBUS messages
you
%MWk+3
Length: number of bytes of the response stored in the buffer parameter (initialization not compulsory to activate the function)
For more information about %MWk+1, refer to Operation and Communication reports.
Example of use
The example relates to reading the output speed of an Altivar 66.
NOTE: It is not necessary to initialize the length parameters before starting the function.