Digital OutPut configuration

Hello BOBILLIER,

1.
On the internet you can find the manual of the Siwarex WP231 module:
https://support.industry.siemens.com/cs/ww/en/view/109770837
In this manual, you can find into the chapter 8.9.3 the assignments for the digital outputs.

My recommendation is to assign the digital outputs one-time with the Siwatool-software.
Here you can see all possible assignments for a digital output.
(See also the attached screenshot of the Siwatool software.)

2.
Attached you can find a TIA V14 Portal example project with a S7-1500 PLC.
(I hope the S7-1200 program is similar.)
Here, you can use the watch table „MODBUS_Watchtable“.

For example to execute the zeroing- or tare-command:

a. Set „MB_MODE“ to „1“ (1 = write)

b. Set „MB_DATA_ADDR“ to „40920“ (40920 = for commands)

c. Set „MB_DATA_LEN“ to „2“ (2 = two words for a command)

d. Set „MB_DATA_PTR[0]“ to „1001“ (= zeroing) or „1011“ (=taring)
Set „MB_DATA_PTR[1]“ to „1“ (= Trigger-flag)

e. Set „REQ“ to TRUE for one-time

3.
The ModBus Address values are in decimal.

4.
Why don't you connect the WP231 to the PLC?
The cable between the WP231 and the load cells can be up to 1000 m.
See also the chapter 13 of the WP231 manual, table "Analog load cell interface connection":
"Maximum cable length between junction box ↔ WP231/WP251 1000 m (3280 ft)"

Best regards

Siwarexi

Hello BOBILLIER,

Attached the TIA V15.1 with a S7-1200 PLC.
I hope, you can open this TIA project.

To your question:
„but i don't understand why you add 40000 to 920 address.“

Well, open the OB1, network 1, and mark the block „MB_CLIENT“.
Press the key „F1“ on your keyboard, so that the information system of TIA Portal is opening.
Now you can see a description of the block „MB_CLIENT“.
Click with the mouse to „MB_DATA_ADDR“.
Now you can see in the table that the hold-registers starts with 40001.
(But please don’t ask me why it’s 40000!?! Unfortunately I don’t know that. Maybe there is an expert in this community, who can explain that for us.)

Best regards

Siwarexi

Hello Eric,

To your questions:

1) I think DB3,DB4,DB5 have no pertinance for my point of interest ?

Yes, you are right!
You can delete DB3,DB4 and DB5!
I used only the DB3,DB4 and DB5 in the past in my TIA test-project for some counters.
Afterwards, I deleted the counters in OB1, but I forgot also to delete the DB3,DB4 and DB5!

2) I suppose than like PLC is Client, WP231 is Server (nativaly)?

Yes, that‘s right!

3) I don't find in your example where you define Server connection parameters (IP-Server, Port,..)

You can find the Server connection parameters (IP-Server, Port,..) in DB2 => CONNECT => RemoteAddress.
My WP231 has the IP-address 192.168.0.21, and the port is 502.

4) In your first reply, you propose me to example to ask one Tare or Zero to WP231. You propose in directly send Trigger- Flag (to 1) in same request than Tare(1001). Is it autorized?

Yes, you are using always the same two Modbus-registers (= 40920 and 40921) to send a command (e.g. the zeroing- or tare-command) or to read or write a datarecord to the WP231.

If you want to read a datarecord:
1. You have to execute the command-code: 2000 + DR-number.
(e.g. you want to read the DR3: the command-code is: 2000 + 3 = 2003)
2.You have to read the Modbus-registers of that datarecord.

(An exception is DR30. Here, you only have to read the Modbus-registers of the DR30.)

If you want to write a datarecord:
1. You have to write new values to the Modbus-registers.
2. You have to execute the command-code: 4000 + DR-number.
(e.g. you want to write the DR3: the command-code is: 4000 + 3 = 4003)

5) I suppose than if there is one reply to reques (like Weight), it's place in MB_Data_Ptr? But in this case how define optimal MB_Data_Ptr size?

Yes, you are right. The data are in MB_Data_Ptr.
Each datarecord (DR3, DR18, ...) has another length. Therefore you have to find out the length of each datarecord.
The size of the MB_Data_Ptr can be find out by this way:
Take a look to the manual of the WP231 module in the chapter 8.
E.g. in chapter 8.4, the DR3 is explained. Here you can find a table.
In that table you can find the length of the DR3. The DR3 starts at the Modbus-register 1000, and ends at the Modbus-register 1094.

6) In your previous example you juste send simple commande to WP231, But if i want to modify Digital Output state, i need send few commandes because i need modify DR18 Registers

See my answer in 4)

(1) Go in Service Mode,(2) Load DR18 i, working memory, (3) Modify DOut State Register,(4) Reload Regiters to DR18, (5) Leave Service Mode.  and between all thoses requests, verify if all is ok and finished through CMD2_STATUT and CMD2_QUIT value.
(1) Service mode is only necessary, when you send the DR3 to the WP231, or you are executing the calibration commands.
(2) Load DR18:

1. You have to write new values (modify Dout states) to the Modbus-registers of the DR18.
2. You have to execute the command-code: 4018
Between all thoses requests, verify if all is ok:
- Modbus-register 922 goes from FALSE to TRUE, when a command executing is finished.
- Modbus-register 923 shows "0", when no error is occurred.

(Maybe it's more easier to connect the WP231 modules directly to the PLC, and to use the Ready-for-use Step7-program from Siemens.  )

Best regards

Siwarexi

Hello Eric,

Well, I recommend you to write at first the four values of your four digital outputs into „MB_Data_Ptr“.
Afterwards you have to write these values to the Modbus-registers of the DR18 with the MB_CLIENT.
After that, you have to execute the command-code „4018“ (= Write DR18).

Best regards

Siwarexi