Single Parameter Access (SPA) Applicaton Layer Note: SPA is used on both Level and Mass Dynamics products. This is a hand-shaking method where the PLC specifies: • parameter number • primary index • secondary index • decimal place • format • read/write flag • value With this method, any value in the Siemens Milltronics product can be read or written. Note: Parameter P999 (Master Reset) is not accessible via the SmartLinx interface on Level products. Using Single Parameter Access (SPA) SPA allows continuous monitoring or demand programming of a parameter. Reading a Parameter 1. Set the Read/Write flag in the output table (Write Block) to 0, “Read”. 2.
Write the Parameter Number, Primary Index, Secondary Index, Decimal Place and Format in the correct locations. Note: If there is no secondary index, then place a 0 in this location. 3. Monitor the Input table of the PLC (Read Block) and watch for the values you wrote to appear in the appropriate locations, then go to Step 4. 4. Read the requested parameter value in the Input table (Read Block). These values are continuously updated. Continue reading from these words until values for other parameters are required. At that time, go back to step 1. Writing a Parameter 1. Set the Read/Write flag in the output table (Write Block) to 0, “Read”. 2.
Write the Parameter Number, Primary Index, Secondary Index, Decimal Place and Format in the correct locations. 3. Write the new value of the parameter into the correct location of the output memory (Write Block) 4. Verify the unit is in program mode (not needed for BW500). For Level see bit 10 of status word in Read Block. Page 20 SmartLinx DeviceNet – INSTRUCTION MANUAL 7ML19981BH02