Joe_ValleyMation Posted June 30, 2014 Report Share Posted June 30, 2014 Hi Everyone, I've implemented Modbus communications with Unitronics Vision series, both serial and Ethernet. I've been able to read and write MIs and MB successfully. But I'm not able to access any other type of addresses. Visilogic help shows a "slave adressing" table. This table apparently indicates for example that in order to read SBs you should read coils starting at 3000 address or in order to read OPLC discrete inputs you should read coils starting at 4000 Outputs->5000 Timer coils->6000 Counters->7000 MBs 3000-4095->8000 (similar story for registers different from MIs) well, this simply doesn't work, reading addresses 3000 or 4000 does not return SBs or Inputs, also any attemp to read a coil address above 4095 will return an error. Modbus offcourse supports 1xxxx addresses for inputs, but Unitronics OPLCS seem to support only 0xxxx (coils) and 4xxxx (registers). There is offcourse the chance to "map" SBs or Inputs to MBs and then read them as MBs, but is not a clean way to do it, and you need to consume MBs just for mapping purposes. I guess there should be a way to read inputs, since there is a "Read Input" function block in Visilogic Modbus Master. So, please tell me I'm wrong and tell how can SBs and Inputs via Modbus from a Unitronics OPlc. Thank You! Joe Quote Link to comment Share on other sites More sharing options...
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.