Siemens Simatic S7-200 System Manual page 117

Bits of the Logic Stack
Load (LD)
Loads a new value (nv) onto the
stack.
Before Load
iv0
iv1
iv2
iv3
iv4
iv5
iv6
iv7
iv8
In these examples, "iv0" to "iv7" identify the initial values of the logic stack, "nv" identifies a new value provided by the instruction, and
"S0" identifies the calculated value that is stored in the logic stack.
Figure 6-5
S7-200 Programmable Controller System Manual
C79000-G7076-C230-02
Basic Concepts for Programming an S7-200 CPU
S0 Stack 0
S1 Stack 1
S2 Stack 2
S3 Stack 3
S4 Stack 4
S5 Stack 5
S6 Stack 6
S7 Stack 7
S8 Stack 8
And (A)
ANDs a new value (nv) with the
initial value (iv) at the top of the
stack.
After Load
S0 = iv0 * nv
nv
Before And
iv0
iv0
iv1
iv1
iv2
iv2
iv3
iv3
iv4
iv4
iv5
iv5
iv6
iv6
iv7
iv7
iv8 is lost. iv8
Logic Stack of the S7-200 CPU
- First stack level, or top of the stack
- Second stack level
- Third stack level
- Fourth stack level
- Fifth stack level
- Sixth stack level
- Seventh stack level
- Eighth stack level
- Ninth stack level
Or (O)
ORs a new value (nv) with the initial
value (iv) at the top of the stack.
S0 = iv0 + nv
After And Before Or
S0 iv0
iv1 iv1
iv2 iv2
iv3 iv3
iv4 iv4
iv5 iv5
iv6 iv6
iv7 iv7
iv8 iv8
After Or
S0
iv1
iv2
iv3
iv4
iv5
iv6
iv7
iv8
6-7