Real numbers

[wizard 0]

For some calculations I need to use real numbers for precision. The problems for me appears when I'm trying to display these numbers on HMI. On HMI I can display only data registers which are INT or DINT. If I'm using real_to_dint() function it approximates the real value to nearest integer and I loose all the information I need. There is a trick to show these real numbers on HMI? And a question related to structured text programming. How can I assign to a data register a DINT value? Example: I have val defined as a DINT variable. D200:=val; doesn't work, I receive the type mismatch error. If I use D200:=dint_to_int(val); it's OK. So, how can I make that the value from val to be written in D200 and D201? I'm using structured text this time, because it's easier to implement the calculations.

[tragically1969 0]

Go on give us a clue, which HMI ?

[Gambit 327]

You can write a little program: With the EBCD instruction its possible to extract the mantissa and exponent. so are able to write a little program to seperate the values before and after the comma. Or if your display can display strings just use the ESTR instrcution to convert real to string Edited 3 Oct 2008 by Gambit

[Veganic 8]

This is not tested: val1 defined as DINT K8M0 := val1; D200 := k4M0; D201 := K4M16; Edited 3 Oct 2008 by Veganic

[wizard 0]

thank both Gambit and Veganic. Veganic, the code is working. I know that k8 is for 32-bit data and k4 for 16-bit data, but exactly does it do? Let me see if I get it K8M0 := val1; writes all bites from M0 to M32 with the binary value of val1 D200:=K4M0; D200 is initialized with binary M0 to M16 D201:=K4M16; D201 is initialized with binary M16 to M32 This is the only solution to move val1 to D200 and D201? In ladder DMOV is enough (eg. DMOV val1 D200 - and it knows what to do). Also, I didn't succeed to use the dmov_m() function with data registers in structured text. dmov_m(m8000, D100, D200); does not work. I receive invalid parameter error. Edited 3 Oct 2008 by wizard

[Veganic 8]

I haven't tested it. Does it work? The idea is : val1 is 32 bit each M is 1 bit. Each K "stands for" 4 bits. K1M0 stands for M0,M1,M2,M3 K2M0 stands for M0,M1,M2,M3,M4,M5,M6,M7. and so on. say val1 = 11101010101010101010101010101010 (32 bit binary reading Bit 0 to Bit 31 - sort of back to front but you get the idea) then K8M0 = 32 bits (8*4 =32) So when K8M4 :=Val1 then M0 =1, M1 =1, M3=1, M4 = 0......M31=0. Take this as two 16 bit words, M0 to M15 is K4M0 and M16 to m31 is K4M16. So D200 = K4M0 = 1110 1010 1010 1010 and D201 = K4M1 = 1010 1010 1010 1010 Edit : let me know if that's not clear. Edited 3 Oct 2008 by Veganic

[wizard 0]

Great, now it's more than clear for me. This is the only solution to move val1 to D200 and D201? In ladder DMOV is enough (eg. DMOV val1 D200 - and it knows what to do). Also, I didn't succeed to use the dmov_m() function with data registers in structured text. dmov_m(m8000, D100, D200); does not work. I receive invalid parameter error.

[Veganic 8]

Hopefully someone will be along with a better solution but it's the simplest I could come up with.

[Digital Diamonds Support 0]

Hello, Solution 1: Define a global variable with type DINT and address D200. Then all you need to do in ST is: GlobalVar := val; Solution 2: Use the IEC address with DMOV_M, as it contains size information (the D after %M means its a double word): DMOV_M(TRUE, val, %MD0.200); This is tested in GX IEC Developer.

[wizard 0]

Great solution, exactly what I was looking for.

[Veganic 8]

I don't have FX3 software yet so was using Q-series. Neither of those option work with the Q.

[Digital Diamonds Support 0]

What software are you using? In GX IEC Developer both solutions work with all Mitsubishi series. Both code lines are compiled to the following machine code (on Q-series): LD SM400 DMOV D6144 D200 (Where D6144 is the address of the variable "val".)

[Veganic 8]

Plain GX Developer. Edit : solution 1 works. Edited 8 Oct 2008 by Veganic