Honeywell HC-900 with Acromag 967EN Modbus/TCP Module as Remote I/O

Transcription

1 Acromag, Incorporated S Wixom Rd, PO Box 437, Wixom, MI USA Tel: Fax: Honeywell HC-900 with Acromag 967EN Modbus/TCP Module as Remote I/O Contents: page Summary 2 Assumptions 3 Requirements 3 Overview of HC Acromag setup 4 HC-900 Modbus setup 8 HC-900 Scaling 15 Testing 17 Notes 23 Acromag manual s Modbus maps 24 Table 1 Acromag indexed hex addresses 26 Copyright Acromag, Inc. Rev 2a, August S. Wixom Rd., Wixom, MI Tel: Trademarks are the property of their respective owners.

2 Honeywell HC-900 Process Automation Controller & Acromag 967EN Modbus-TCP module as remote I-O Summary: The Acromag 967EN has 8 analog 4-20mA inputs. It is a Modbus/TCP slave, ideal for use as remote I/O with a Honeywell HC-900 Hybrid Controller (Process Automation Controller) that runs as a Modbus/TCP master over a standard Ethernet network connection. The Acromag 967EN provides data in either floating point or signed integer formats. Floating point values can be scaled to engineering units in the Acromag and read directly as scaled values. If the scaling in the Acromag is correct, no scaling is needed in the HC-900. Signed integers values are ranged 1 to 20,000 counts across the 4-20mA input span; so scaling to user-friendly engineering units has to be done on the HC-900i. Acromag setup is done via web browser, no software is needed. Typical input and scaling setup changes made in the web browser are downloaded and executed quickly, on the order of seconds. An ON-OFF power cycle is not required for input configuration changes. Acromag's sample time is 8mS, so the Acromag data tends to be noisier than the same signal wired into the HC-900. The solution is to let the Acromag average multiple samples. Start with 20 as a number to average with. The 200 ohm 4-20mA input resistance will not unduly load a loop powered circuit, but will inhibit HART communications (HART requires 230 ohms, minimum). Acromag s i2o remote messaging function writes values only to other Acromag products. Hence, i2o is not applicable for use with the HC

3 Assumptions: The implementer has - familiarity configuring the HC-900 using Honeywell s Hybrid Control Designer (HCD) software, the HC-900 s development software; function block configuration, loading configurations, etc. - familiarity with ethernet network connections (devices on the same subnet) - familiarity with engineering unit scaling of industrial signals Requirements: From its introduction in 2002, the HC-900 has supported Modbus/TCP. Serial Modbus Master functionality was added to Honeywell HC-900 s in June This note covers Modbus/TCP connections, only. It is strongly advised that the latest hardware firmware revision be used for communications. Firmware updates are available at no cost on Honeywell s public web site. Overview of HC-900 Modbus master functions: All HC-900 controllers have an Ethernet port, E1, that can be used as a Modbus master with the appropriate function blocks. The Modbus master issues a Modbus request to the Acromag Modbus slave for data. The Acromag s response can provide from 1 to as many as 62 Modbus values in one Modbus message (model 967EN handles 8 analog signals). The data values polled by Modbus/TCP that reside in HC-900 tags and can be used in any fashion that any HC-900 tag can be used. The Modbus/TCP sourced tags are updated once per second. All the configuration parameters done in the Acromag s web browser can be done via Modbus, but this app note only addresses the critical function of fetching data from the Acromag. HC-900 uses hexadecimal Modbus addressing, not decimal register values. 3

4 Acromag Setup: Power the Acromag (24Vdc). Plug in an Ethernet cable, straight CAT5 cable to PC works OK (crossover not needed). Assign the Acromag a working static IP address - The Acromag default IP address is Get your PC s ethernet port onto the same subnet: x - Launch a web browser (Internet Explorer) - open log-in default user: User (capital U) default password: password00 (lower case,.... zero zero) - Browse to the Network Configuration web page - Enter the working IP address ( in this example) and click submit button - Change PC s IP address to get it back to its working subnet ( xx in this example) - Log back into the Acromag on its new working IP address/subnet via browser User: User 4

5 password: password00 - Navigate to the Input Configuration web page - Select a channel (each channel is independently configured) - Select input type (typically 4-20mA) - If reading floating point, Acromag s scaling can be used effectively. Enter the zero and span range scale values. The floating point values are IEEE 754 format, totally compatible with the HC-900. Both Honeywell and Acromag offer all four byte order formats, which, of course, must be matched. Floating Point control on page 11 has a table for matching byte order. 5

6 - If reading integer formatted values, Acromag s scaling has no effect. The Acromag s integer values are 0-20,000 ranged over 4-20mA range. So, when reading integer format, skip the ranging. The use of integers will require engineering unit scaling on the HC Submit: click Channel Configuration Submit Average: - average 20 samples, submit Floating Point Control: (do not enable if reading integer format) - Select Enable Floating Point Support; submit - Select floating point byte order B1,B0,B3,B2 which corresponds to HC-900 s default FP B byte order - be sure to fill in the scaling values for the input range (example gpm), submit Conclude by submitting latest or all changes: 6

7 HC-900 Modbus setup: Screen shots and description shown below are from a C30 controller. The setup for all model controllers, C30, C50, C70 is the same. 1) Confirm that HC-900 controller is on the same subnet (xxx.xxx.xxx.yyy) as the Acromag. In this example, the HC-900 is at ; the Acromag is at HC-900 Ethernet port setup: 2) Configure the Modbus master to read the Acromag - launch HCD software - open the configuration file (.hcd) to be used - Add and configure the Modbus master function blocks, and if needed, the free form math blocks for scaling. 7

8 a) The TPCS Modbus Slave TCP function block is required for a Modbus master read operation for a given slave. Each slave requires a separate TCPS function block. TCPS TCPR The TCPS block can read up to four values which are tagged on outputs RD1 through RD4. If more than 4 values are need, then the Modbus TCP Read function block (labeled TCPR) can be used to read additional values from the same slave. - The input at the top of TCPR must be connected to the output at the bottom of TCPS. - Each of the RDx outputs needs a tag. - The TCPS block must be enabled (ENABLE pin only; EN 1 to EN 4 enable writes). On-line Help files are pop-up by right clicking the function block and selecting Help: 8

9 The tags in the example below are follow an arbitrary convention: Acromag channel #_format_function code where the format is either floating point (FP) or signed integer (INT) and the function codes are either Read Input register (04) or Read Holding Register (03). b) Configure the TCPS function block General tab (double click the function block) 9

10 - Give Slave Tag Name an appropriate friendly name (ACROMAG_967EN for example) - Modbus/TCP Addresss = Acromag IP address - The HC-900 default Modbus double register format is FP B. - HC-900 s FP B is compatible with Acromag s B1, B0, B3, B2 byte order. Table: HC-900 byte order format vs Acromag byte order format Honeywell FP B FP LB FP BB FP LB Acromag B1 B0 B3 B2 B3 B2 B1 B0 B0 B1 B2 B3 B2 B3 B0 B1 A mismatch of byte orders produces grossly unusable results. Check the byte order shown on the Acromag s input configuration web page. It s quicker to change it there than an HC-900 upload. Important Note: Selecting integer format mandates (requires) HC-900 scaling of the 0-20,000 count data value provided by the Acromag. Selecting floating point format can use the Acromag s scaling, as shown above in the Acromag setup. The HC-900 s free form math block has only one output, so each integer analog value requires a free form math block for scaling. My recommendation is to use floating point and let Acromag scale the data. 10

11 c) Open the TCPS function block Read tab (below) and configure - the address - data format (Register Data Type) - Modbus Function code (read Input register 04 or Holding register 03) The example shows: - channel 00 at address 11 (hex) as an integer read by function 04 - channel 01 at address 21 (hex) as a floating point value read by function 04 11

12 d) If needed add the TCPR block for additional read values. The TCPR function block properties summarize - the addresses for channels 00 and 01 - for Read Input register function code 04 and Read Holding register function codes 03 - reads in both signed 16 bit integer data format and floating point data format Address: use the address table below or calculate the address Acromag s Modbus map in the manual omits the hexadecimal addresses for use of Holding register function code 03 (manual says remapped to 43xxx ). Note that when calculating an address using the decimal register value, the leading 3 or 4 is assumed, neither is not used in calculating indexed addresses. The formula for converting involves the dreaded Modbus one offset, the difference between register decimal locations and hexadecimal addresses. The formula is Indexed decimal register value converted to hex, then subtract one. 12

13 Example: channel 05 uses decimal register for floating point format when the input register is read by function code 04. To read the channel 05 from a Holding register in floating point using function code 03, the register is at 43044, offset into the 43xxx memory range is an index of 3044 decimal (where the leading 4 is assumed and ignored) 3044 decimal = BE4 (hex) BE4 (hex) minus one = BE3 The indexed offset for channel 05 using function code 03 is BE3. Channel 05 data at register (decimal) is fetched from indexed address BE3 (hex) Whether one subtracts one from the register value before converting to hex, or after, makes no difference. The table below shows the hex addresses in the HC-900 column for using Holding register function code 03 13

14 Scaling The HC-900 s free form math block can be used for scaling integer data In this example, a channel s count value (0-20,000) is divided by 50, resulting in a value in gpm engineering units. 14

15 Typical configuration with scaling: 15

16 Testing: Acromag Acromag s Test page shows real-time, live updates of the analog input signals and the scaled conversion values, which are the values that should appear when reading floating point values in the HC

17 Testing: HC-900 HCD s Monitor mode displays a tag s real-time value in green. The monitor mode is enabled from the Eye tool icon, outlined in red below, and assumes a network connection to the HC-900 controller: Clicking a tag displays the real-time value of the tag along with the engineering units in green: 17

18 Dragging the mouse cursor over the function block inputs/outputs shows values minus the engineering units: If the floating point values don t match the scaled input values on Acromag s Test page, something s wrong. 18

19 Modbus port diagnostics monitor > Modbus Port Diagnostics > Modbus/TCP Port Diagnostics 19

20 Modscan32: A generic Modbus master application, like Modscan32 reads Acromag Function Code 04, read Input Registers: Note that the integer value at is counts, equivalent to 12.0mA. The floating point register at is scaled to engineering units in gpm 20

21 Function Code 03, read Holding Registers: Note that the integer value at is counts, equivalent to 12.0mA. The floating point register at is scaled to engineering units in gpm: 21

22 Notes: 1) The Acromag 967EN is a Modbus/TCP slave in a desktop test easily supported two Modbus/TCP connections from two Modbus masters (HC-900 and Modscan32, each at one second polling rates). 2) Analog input calibration can be done on the Acromag, or a 'loop calibration' can be done with HC-900 s free form math block using either - an offset factor ( + term) - an offset (+ term) and a slope scaling factor (* term) to produce y=mx+b. 4) Differences between commercial and industrial Acromag modules: 5) References to HC-900 s Modbus maps are irrelevant because the HC-900 runs as a Modbus master. 6) Honeywell manuals are available on Honeywell s public web site. Those that reference Modbus master operation are HC900 Hybrid Control Designer Function Block Reference Guide, document number has specifics on the function blocks. HC900 Hybrid Control Designer User Guide, document number covers using the HCD software. 22

23 Acromag manual references Data representation: Modbus register maps: A) Input registers read with function 04 Data values in integer format reside in Input registers starting at decimal Data values in Floating point format reside in Holding registers starting at

24 Holding registers are the identical to input register values remapped to 43xxx : Which is nice, but the HC-900 does not use decimal register values, it uses indexed hexadecimal addresses. See Acromag s manual for indexed hex addresses for 04 read Input registers function code. See the Table 1 (next section) for indexed hex addresses for 03 read Holding registers function code. Table 1 Acromag 967EN slave indexed Hexadecimal addresses for use with HC-900 when using 03 function code (read Holding registers) Application note courtesy of Dan Weise, Lesman Instrument Company 24

25 About Acromag Acromag is a leading manufacturer of temperature transmitters and signal conditioners for use with thermocouple and RTD sensors. These instruments convert the sensor input to a proportional 4-20mA DC current, DC voltage, Modbus, Profibus, or Ethernet signal to interface with a PC, PLC, DCS, or other control equipment. Acromag has designed and manufactured measurement and control products for more than 50 years. They are an AS9100 and ISO 9001-certified international corporation with a world headquarters near Detroit, Michigan and a global network of sales representatives and distributors. Acromag offers a complete line of industrial I/O products including a variety of process instruments, signal conditioners, and distributed fieldbus I/O modules that are available with a 7-year warranty. Industries served include chemical processing, manufacturing, defense, energy, and water services. For more information about Acromag products, call the Inside Sales Department at (248) , FAX (248) sales@acromag.com or write Acromag at South Wixom Road, P.O. Box 437, Wixom, MI USA. The web site is 25