Modbus - Serial Port UART

[CodeBanger]

I have 2 computers in which the serial port does not work over Modbus. One of them is a laptop and one is a regular PC. Other computers work fine. I use the same cable, same 984 device and try communication from both Windows 95 and from the dos prompt. I suspect it is something to do with the UART type. Does anyone know why this would be. Thanks in advance.

[meirs]

It is not MODBUS - it is the software that communicates - maybe it (the software) doesn't handle the UART in question properly. So please tell us which software it is (the fact that it implements MODBUS is irrelevant to your problem). MODBUS is just a protocol defined by a piece of paper (PI_MBUS_300).javascript:emoticon('') smilie

[Guest Phil]

The problem you are having lieswithin the laptop, since the version of windows you are using is 95 (rev?) handles the comm port much differently than a standard computer or desk top, fundamentally the laptop does not maintain the port open unless data is continually being sent across it. Also 95 should be replaced with Windows ME which handles comm. ports much differently than 95/98/98se/wnt/win2000/xphome/XPPro, M.E. holds the port open since M.E. looks at the comm ports as dedicated I/O. Hope this helps. Sincerely Phil

[Crossbow]

One thing I was always told by Modicon was if your laptop is set up to automatically allocate it's devices in BIOS, it might not work. Check your BIOS setup, and if the setup for the serial port is AUTO, change it to COM1 or COM2 or wherever you like. Another thing I've seen in the past is make sure the computers BIOS is up to date. Omron's software used to hate Toshiba computers, until they fixed their BIOS.

[CodeBanger]

Thank you for the replies. The software I'm using is Modsoft 2.62 to connect to a 984 device and XBT-L1000 with XBT L1MOD01 driver to connect to a Magelis P022010. I've heard that laptops can be a problem. The laptop in question runs Windows 98. What is curious is that the desktop that runs Windows 95 also does not want to connect. I have tried to connect both computers from Dos mode. The laptop is an IBM thinkpad 600e. I've done the Bios upgrade. I will try the suggestions and let everyone know what happens.