Powerful Solutions for Digital Plants
MYNAH Technologies 504 Trade Center Blvd. Chesterfield, MO 63005 Telephone 636 681-1555 Fax 636 681-1660
www.mynah.com
4
2
THEORY OF OPERATION
As part of the serial interface port license, a standard Modbus protocol is installed on the
DeltaV PSIC prior to customization. The PSIC needs to be flash upgraded from the
Modbus protocol to the Allen-Bradley protocol before operation.
The Allen-Bradley serial driver implements DF1 protocol. It communicates with PLC-3,
PLC-5 or SLC5/XX devices on the DH+ network through either a 1785-KE or 1770-KF2
communication modules. These modules convert the DF1 serial protocol to the DH+
network protocol. The switch settings must be configured properly for the RS-232 or RS-
422/485 prerequisite for proper operation.
The Allen-Bradley Driver communicates with the PLC and updates emulated DeltaV I/O
with the data received from the PLC. The primary functions of the driver are listed below:
·
Performs data and message handling between DeltaV and PLC-3 / PLC-5 / SLC5/XX.
·
Sends messages to PLC-3 / PLC-5 / SLC5/XX from DeltaV
·
Processes reply information and updates the corresponding emulated DeltaV I/O
channels
·
Update emulated input channel status and Data Block status to indicate the
communication state of PLC-3 / PLC-5 / SLC5/XX.
·
Checks validity of messages received by PLC-3 / PLC-5 / SLC5/XX.
Upon proper installation and configuration of the Allen-Bradley driver within the
DeltaV/PSIC system, communications with a properly configured Allen-Bradley PLC-3 /
PLC-5 or SLC5/XX may proceed.
There are a maximum of 16 Datasets (DS) per port, with a total of 32 per PSIC. The
maximum number of data elements per Dataset that can be supported by the PSIC
depends on the data file type. Note that the number of supported Datasets does not
change. The following table describes this correlation:
Dataset Data File Type
Number of Data Elements
or Registers
Boolean 100
Discrete 100
8-bit signed integer
100
16-bit signed integer
100
32-bit signed integer
50
8-bit unsigned integer
100
16-bit unsigned integer
100
32-bit unsigned integer
50
Floating point
50
String 1
The DeltaV PSIC is the master in all communications. It polls each input device and
requests data values on a message by message basis. The output is performed when a
new value is to be written to the devices. The PSIC constantly scans the configured input
Datasets for new values and updates the database. Upon a change of value in the output
Dataset, the PSIC will finish the current input scan and suspend the input process. It will
service all the output requests before resuming the input process.
