ABB PGC5000 Generation 2 - Modbus Configuration Recommendations

100 | PGC5000 GEN 2 | 892 J006 MNAH
⎯ Specify the register format for each tag by appending the keyword followed by the optional
scaling limits such as:
• Analyzer.Schedule.Process Stream.Propane.Concentration,01,31000,INTEGER
• Analyzer.Schedule.Process Stream.Methane.Concentration,01,31001,FLOAT
• Analyzer.Schedule.Process Stream.Hexane.Concentration,01,31003,Scaled0-
9999,0.0,100.0
• Analyzer.Schedule.Process Stream.Isobutane.Concentration,01,31004,Scaled0-
4095,0.0,100.0
The following analog tags are always represented as INTEGER values:
⎯ Analyzer.Oven.DTC1.ZonesActive
⎯ Analyzer.Oven.DTC2.ZonesActive
⎯ Analyzer.Oven.EPC.ZonesActive
⎯ Analyzer.Schedule.Stream.CycleTime
⎯ Analyzer.Schedule.Stream.LastReportType
⎯ Analyzer.Schedule.Stream.Component.UnitsOfMeasure
The Analyzer.Schedule.Stream.SampleTime tag is represented in two different formats by appending
the keyword TIMESTAMP1 or TIMESTAMP3 to the .csv entry. The TIMESTAMP1 format uses a single
MODBUS register containing the hours in the high byte and the minutes in the low byte. TIMESTAMP3
uses three registers with the first containing the hours, the second containing the minutes, and the
third containing the seconds.
The Analyzer.Schedule.Stream.NewDataReady tag is set whenever data is received for the specified
stream. It is reset by the MODBUS master prior to the next analysis becoming available or configured
to automatically reset after a configured number of seconds. To configure the tag to reset
automatically, append a delay counter (in seconds) to the .csv entry.
⎯ Example: Analyzer.Schedule.Stream.NewDataReady,01,11002,5. This results in the
NewDataRead bit to reset after five seconds.
5.8.3 Modbus configuration recommendations
The PGC5000 Series Master Controller supports a Modbus TCP interface (acting as slave). This
interface is used to communicate with control systems. When configuring the Modbus master interface
to the PGC5000, ensure that you don’t poll the analyzer more than needed. Illogical configuration of
the Modbus master can result in resource issues with the PGC5000, which can lead to unpredictable
behavior. On software V3.0.3.13 and newer, the maximum response time of the Modbus is set to 50
ms.
To enable the poll delay feature, add a line of code to the Modbus map. An example is shown below.
Add the code to the MODBUS.CSV map in the PGC5000 GEN2 working folder:
format\Configuration\Working. Ensure that the software is V4.2.1.25 or newer. The added code used
in the correct software version will clear the high polling error that occurs when the DCS is polling the
PGC5000A controller more than 1 time a second.
Code description: PGC5000name.PollDelay,1,time in milliseconds,
⎯ Example: 310-AT-1301_SO123456-010.PollDelay,1,1000
IMPORTANT NOTE: There is no space between “Poll” and “Delay”.
The example above would be for every second.
The following general guidelines are recommended when configuring the interface:
⎯ When both networks are connected to one control system, use the secondary network only for
failover. The analyzer network is designed for all normal network traffic to be on the primary
network. Use the secondary network only upon failure (inability to communicate) with the
primary network.
⎯ Read the NewDataReady tags to determine when report data has changed, rather than polling
for all report data continually. In a typical analyzer, data may not change for 6-10 minutes
(cycle time of analysis). Polling for report data at a sub-second interval places an undue load
on both the PGC5000 and the control system. Polling rates from master connections should be
1 second or greater.
⎯ Group transactions as much as possible. Use function codes 1,2,3,4 to perform reads of blocks
of data. This is a more efficient use of each packet of data. A read of 2 registers 10 times (10
transactions, 40 bytes) is much more costly of CPU time, for both the control system and
PGC5000, than a read of 20 registers once (1 transaction, still 40 bytes).