step 5 analog values

[Mohamed Metwally]

how to read analog input values in siemens step 5?
In other words if i want to know the analog input value from the program i always find analog values in DW but i don't know what to do to know this value.

 

[Mohamed Metwally]

how to read analog input values in siemens step 5?
In other words if i want to know the analog input value from the program i always find analog values in DW but i don't know what to do to know this value.

Please can u send me private messages for the answer

 

[JesperMP]

Hi Mohamed Metwally.

As far as I remember, there are two system function blocks, FB250 and FB251 for reading from and writing to analog i/o.
These blocks would take care of scaling as well.

 

[Mohamed Metwally]

forcing analog values in step5

how to force analog values in step 5

 

[parky]

Depends on plc 115 or 155 etc.

115 have in-built blocks the others don't.

however the peripheral word is set up as lowest 3 bits are not data but info bits

bit 0 = overflow, bit 1 = ident bit bit 2 = activity bit

bit 15 = sign bit

all the rest are the analog value

so

l pw 128

t Fw 200 (store sign & other bits)

slw3 (remove sign)

srw4 (then remove lower bits)

t fw202 store analog raw value

you can then use the bits in fw200 for sign & if required diagnostic bits
there are some differences betweeen U block & A/K range of cards
hope this helps

 

[PeterW]

slw3 (remove sign)

 

[b16mcc]

Wouldn't that be

SLW 1
to simply remove the sign bit and then
SRW 4
to remove the info bits.

 

[uptown47]

Wouldn't that be

SLW 1
to simply remove the sign bit and then
SRW 4
to remove the info bits.

That's what I thought. I think the slw 3 was a typo and parky meant slw 1.

;-)

 

[parky]

Yep your right it was a typo, it's a bit old this thread?

 

[uptown47]

Christ!! You're right!
Still, it just shows... the typo-police will catch up with you eventually.. it may not be today, or tomorrow, but definitely within the next 5 years ;-))

 

[PeterW]

I was too sacarstic to actually say anything in them days, still as I know Parky I knew it was a typo

 

[parky]

Yep Peter is was & even if it wasn't I would have said it was.
I'm getting old now so the grey matter is a bit slow anyway this thread is about as old as S5 lol