Skip to Content

Register Login

Industry Online Support

Technical Forum

Navigation

Modbus RTU communication to Sentron PAC3200

Created by: Abyrne at: 8/6/2010 5:57 PM (2 Replies)

Rating (2)

Thanks 3

3 Entries

8/6/2010 5:57 PM	Rate (0)
Abyrne Bronze Member Joined: 11/26/2008 Last visit: 12/8/2023 Posts: 101 Rating: (4)	Hello, I have a S7- 1214 CPU connected to a Sentron PAC 3100 via Modbus RTU. I am trying to access Total active power Total reactive power (VAR1) How do i set up a DB to monitor the values in these registers? How do i reference the register in the PAC that holds this data? (i.e. what part of the DB do i access?) Thank you for your help

Suggestion To thank Quote Answer

8/9/2010 8:35 PM	Rate (2)
jklm Platinum Member Joined: 12/22/2006 Last visit: 1/25/2022 Posts: 1742 Rating: (309)	Hello, In this Manual (Manual SENTRON Expansion Module PAC RS485), you will see at p.35 that the registers for the values you mention are: start register 63, 2 regsiters wide: Total Apparent Power value type: Float Unit: VA start register 65, 2 regsiters wide: Total Active Power Float W These can be read using the Modbus function code 3 or 4 A float is 32 bit wide, and a modbus register typically 16 bit wide. Therefore two consecutive registers are used. In the S7-1200: The MB_COMM_LOAD function block configures a port on the Point-to-Point (PtP) CM 1241 RS485 or CM 1241 RS232 module for Modbus RTU protocol communications. The MB_MASTER function block allows your program to communicate as a Modbus master using a port on the Point-to-Point (PtP) CM 1241 RS485 or CM 1241 RS232 module. The MB Master has the following parameters (among others) MODE: Mode Selection: Specifies the type of request: read, write, or diagnostic Mode 0 allows to read registers (see page 191 of the system manual of the S7-1200) DATA_ADDR: Starting Address in the Slave: Specifies the starting address of the data to be accessed in the Modbus slave. If you use 30063 as data_addr, you will read starting from register 63 DATA_LEN: Data Length: Specifies the number of bits or words to be accessed in this request. Here you specify 4 registers (to read from 63 to 66 at once and get both data with one request) DATA_PTR: Variant Data Pointer: Points to the CPU DB address for the data being written or read. The DB must be a "NOT symbolic access only" DB type. Here I would try to define a DB with a named structure with the two floats in it.
	Best regards jklm Suggestion was helpful? Feel free to rate it.
Suggestion To thank Quote Answer
This contribution was helpful to 3 thankful Users Abyrne Reva P farah.moh

7/7/2016 3:25 PM	Rate (0)
Min_Moderator Platinum Member Joined: 9/3/2014 Last visit: 3/13/2019 Posts: 4766 Rating: (122)	New question published by AutoGen_1020194 is split to a separate thread with the subject CB1241 connection to PAC 3100. Best regards Min_Moderator

Suggestion To thank Quote Answer

|

Share this page:

Share this page on...

Follow us on