5/20/2020 3:19 PM | |
Joined: 5/30/2014 Last visit: 10/7/2024 Posts: 148 Rating: (18) |
Hi, In document from modbus.org MODBUS over Serial Line Specification and Implementation Guide V1.02 (Modbus_over_serial_line_V1_02.pdf), on page 27 stands:
These statements are from the year 2006 and look like minimal number of devices, not maximal. So, I am still confused. Besides that, here is a paper from Texas Instruments (bus driver manufacturer), which explains how to multiply number of devices (up to 256): RS-485 Unit Load and Maximum Number of Bus Connections Does anybody from Siemens BT know the answer? |
Last edited by: C-3PO at: 05/20/2020 15:20:13small change Last edited by: C-3PO at: 05/20/2020 15:21:00small change Last edited by: C-3PO at: 05/20/2020 15:23:23Last edited by: C-3PO at: 05/20/2020 15:24:21small change Last edited by: C-3PO at: 05/20/2020 15:34:40If you find my contribution helpful please RATE it :)) |
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9/28/2023 1:46 PM | |
Joined: 3/1/2018 Last visit: 10/7/2024 Posts: 56 Rating: (22) |
Hi, As Bill mentioned RS485 tranciever is limited to 32UL (unit load). Please find attached TI application sheet for RS-485 Unit Load and Maximum Number of Bus Connections. I have a network with 32 Modbus devices and PXC5.003 as integrator. Current load stated in diagnostics tab is approx. 55% and max current load is approx. 70% so I asume we could add more units and it should work without problem. I was also courious of this limitation and will test with more units on my next project. AttachmentREN_rs-485-transceiver-tutorial_WHP_20180809.pdf (358 Downloads) |
Best regards, |
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