Help on hex thing ;=)

In a Siemens S7-400 i have the following in a DB :

DB1.DBB 127 = 78
DB1.DBB 128 = 80
DB1.DBB 129 = 00
DB1.DBB 130 = 01
DB1.DBB 131 = 27

Ofcause the values change some times when new data arrives(via RS232).

The values are in hex - but the thing is the number i need from the example above IS 7880000127 in real world numbers

So how do i get from the hex stuff over, and get them together in one ?

try BCD_INT or bcd_DINT

The value are in BCD in think. So you can convert word by word with the instruction BCD_INT

DB1.dbw128 -> BCD_INT -> MW0

DB1.dbw130 -> BCD_INT -> MW2

DB1.dbw132 -> BCD_INT -> MW4 (be carefull, DB1.DBb132 must be 0)



Check that you have the right value in MW0, MW2, MW4. If it's not correct you may have to swap db0 and db1 (same for the other byte) in a temporary word before convert in INTEGER



After you have to do

MD10 = MW0 + MW2 * 1000 + MW4*1000 0000

To give a definitive answer, we need a bit more info.

Having said that, 5 Bytes of data is not a normal form for representing a number (other than as ASCII text). The normal formats are Byte, WORD (Integer) and DWORD (double precision Integer or REAL).

You can get an idea of the possibilities if you look at the values in a VAT. Normal convention is to start WORDS and DWORDS on an even boundary address, so try looking at DB1.DBB128, DB1.DBW128 and DB1.DBD128 and see what shows up. In the latter case you can change the display format from decimal to REAL and see if anything makes sence.

Otherwise, let us know where the data is coming from (and why you reckon the interesting area begins at DBB127), and what you want to do with it.

What sort of real world numbers do you require ?

If you want an integer then the biggest signed integer you can store in a double is word is 2147483647

If you want a floating point number then you will lose some precision.

What processing are you going to do with the resultant numbers ?

Cta said:

The value are in BCD in think. So you can convert word by word with the instruction BCD_INT

DB1.dbw128 -> BCD_INT -> MW0

DB1.dbw130 -> BCD_INT -> MW2

DB1.dbw132 -> BCD_INT -> MW4 (be carefull, DB1.DBb132 must be 0)



Check that you have the right value in MW0, MW2, MW4. If it's not correct you may have to swap db0 and db1 (same for the other byte) in a temporary word before convert in INTEGER



After you have to do

MD10 = MW0 + MW2 * 1000 + MW4*1000 0000

Click to expand...

That did the trick - thanks all !

So was your example not actually an example ?

Dont know what you mean ??

I found out that i only needed the first XXXX and the last XXXXX(1-99.999), so this is what i did and it works great :

OPN #Send_DB // Open data DB


L DBB 127 // Load the first data byte
BTD // Convert from BCD to double int
L L#10000000 // Move into place
*D
T #Tmp_DINT


L DBB 128 // Load the second data byte
BTD // Convert from BCD to double int
L L#100000 // Move into place
*D
L #Tmp_DINT
+D
T #Tmp_DINT


L DBB 129 // Load the theird data byte
BTD // Convert from BCD to double int
L L#1000 // Move into place
*D
L #Tmp_DINT
+D


L 10 // Move out X to get ID from 1-99999
/D
T #Tmp_DINT


L DBB 130 // Load the fourth data byte
BTD // Convert from BCD to double int
L L#10 // Move into place
*D
L #Tmp_DINT
+D
T #Tmp_DINT


L #Tmp_DINT
L 10 // Move back for last byte
*D
T #Tmp_DINT
L DBB 131 // Load the fifth data byte
BTD // Convert from BCD to double int
L #Tmp_DINT
+D
T #ID_No // Output ID number

Coralreef said:

...but the thing is the number i need from the example above IS 7880000127 in real world numbers

Click to expand...

Your posted code produces the number 788000127 - hence my confusion.

SimonGoldsworthy said:

Your posted code produces the number 788000127 - hence my confusion.

Click to expand...

Ahh okay - well that changes all the time

Its a code comming from a tag read by an RS232 ID reader !!