Reference MVI56-DH485R
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ControlLogix Platform
User Manual
DH485 Interface Module for Remote Chassis
ProSoft Technology, Inc.
Page 67 of 97
August 27, 2009
With the configuration displayed above, requests for file 10 elements 0 to 99 will
be associated with the module’s internal data registers 0 to 99 and file 12
elements 100 to 199 will be associated with the data base registers 100 to 199.
The module supports up to 50 of these data mappings. When a request is made
of the slave driver, the mapping defined in this override section will first be
searched first. If the data area in the request is found in the list, that data
mapping will be utilized. If the data area in the request is not found in the list, the
fixed data area mapping will be used.
5.2.6 CIF Data
The module supports the common interface file (CIF) of the DH-485 protocol. A
separate data area can be defined for each application port. This data area is
divided into read and write data and is mapped into the module's internal
database. The module's application constantly transfers the read CIF data from
the CIF database to the module database and the write CIF data from the
module to the CIF database. The parameters used to define the CIF database
are contained in the configuration file. This optional feature of the module should
only be utilized if required by a remote master on the network. Otherwise, the
data file functions (500CPU message) instructions should be used to access and
control the module's data. The following diagram shows the relationship of the
DH-485 drivers, the CIF database and the module's database:
Module
Database
Write
Function
Read
Function
Master Driver
Write
Function
Read
Function
Slave Driver
CIF
Database
Request
Response
Request
Response
Request
Response
Request
Response
Read Database
Read Database
Write Database
Write Database
Write CIF Request
Read CIF Request
CIF Write Data
CIF Read Data
Important: The user can configure the size of the CIF Read area through the "CIF
Read Count" parameter. The size of the CIF write area is given by following
parameters"
CIF Write Count = 244 - CIF Read Count.