MVI46-MCM FC2 is overwritng next FC2 with 1st FC2 data
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brucelester
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Friday 09 March 2007 11:06:23 am |
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MVI46-MCM FC2 is overwritng next FC2 with 1st FC2 data
Had similar problem with FC1 but was able read inputs with one command. I need to read 480 consecutive bits. when I increase count to more than 192 bits it fails. When I read the next set of 192 bits or 12 words the data appears but it is overwritten with data from first read. First set begins @ 00113 count 192, second set begins @ 00305 count 192.
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jsanders
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Friday 30 March 2007 3:46:58 pm |
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RE:MVI46-MCM FC2 is overwritng next FC2 with 1st FC2 data
While the module emulates the addressing scheme of Modicon processors, it does not keep separate data areas for each data type. Coil addresses 0001-0016 use the 16-bits of storage in module memory register 0. Input Status bits 10001-10016 use the same register 0. Input Register 30001 and Holding Register 40001 also use the same module memory register 0. Bit level commands use internal addresses specified as bit numbers and register addresses are specified by register number.
For instance, the 16 bits of module memory address 100 can be accessed with FC 1, 5, or 15 as Coil addresses 01601-01616; with FC 2 as Input Status 11601-11616; with FC 4 as Input Status Register 30101; or with FC 3, 6, or 16 as Holding Register 40101. As you can see, if you are not careful in the way you create your command configurations, it would be easy to have data from one command overwrite data from/for another command.
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