Siemens SIMATIC S7-200 System Manual page 463

Example of DP Communications to a CPU
Technical Specifications
Network 1 //Calculate the Output data pointer.
//If in data exchange mode:
//1. Output buffer is an offset from VB0
//2. Convert Vmem offset to double integer
//3. Add to VB0 address to get output data
// pointer.
LDB= SMB224, 2
MOVD &VB0, VD1000
ITD SMW226, AC0
+D AC0, VD1000
Network 2 //Calculate the Input data pointer.
//If in data exchange mode:
//1. Copy the output data pointer
//2. Get the number of output bytes
//3. Add to output data pointer to get
// starting input data pointer.
LDB= SMB224, 2
MOVD VD1000, VD1004
BTI SMB228, AC0
ITD AC0, AC0
+D AC0, VD1004
Network 3 //Set amount of data to be copied.
//If in data exchange mode:
//1. Get number of output bytes to copy
//2. Get number of input bytes to copy
LDB= SMB224, 2
MOVB SMB228, VB1008
MOVB SMB229, VB1009
Network 4 //Transfer Master outputs to CPU
//outputs. Copy CPU inputs to the
//Master inputs. If in data exchange mode:
//1. Copy Master outputs to CPU outputs
//2. Copy CPU inputs to Master inputs
LDB= SMB224, 2
BMB *VD1000, QB0, VB1008
BMB IB0, *VD1004, VB1009
Appendix A
449