Search Bit

How to search bit 16 bit data register from LSB to MSB in fx series of mitsubhishi plc.

We will need to know what software you are using GX or IEC before we can help, and what do you mean from LSB to MSB.

Badger said:

We will need to know what software you are using GX or IEC before we can help, and what do you mean from LSB to MSB.

Click to expand...

LSB = Least Significant Bit
MSB = Most Significant Bit

He wants to search a 16 bit word from one end to the other and find the bit that is True (or False, I guess).

Still need to know which software version he is running. I suspect its quite late in India and we wont know till tomorrow. Thanks for the LSB/MSB info Tharon.

Try BON instruction this gives a check on specified bit status in a word although this may not be what you want, to check which bit is on i.e. step though bits in word till a bit is "1" then use a loop, load a 2 registers with 1
"WAnd" reg1 with the word if result <> 0 then this bit is set
multiply reg1 by 2 and add 1 to reg2 then try again.
when you reach 16 count then exit loop.
reg 2 will contain the bit No. that has the "1"
Sorry can't give you an example no Gx or IEC here at the moment
but it may go something like this:

mov k1 d1 // move 1 to D1 & D2
mov k1 d2
Label2 // jump back label
wand d1 d3 //and the word to check (D3) with D1
<> D3 K0 CJ P1 //if result <> 0 then bit must be set (D2 = bit no)jump to P1
mul D1 K2 // mask for next bit
ADD D2 K1 D2 //add the bit pointer
< D2 K16 CJ P2 //if bit pointer < 16 then jump back
Label1

there are many ways of checking for bits in a word you could shift one place to bit 0 then test this bit.
I'm sure someone here could knock up a quick bit of logic or check the instructions in the manual

Yes i wants to search a 16 bit word from one end(right) to the other and(left) also from left end to right end.

e.g if D0 = 0001 0101 0011 0100 (this 16 bit word i want to check)
Then i want result in D1=2 (bit search from right to left)
D2=3 or 12 (bit search from left to right)

The software i am using is GX developer.

Hope this may help this works msb to lsb