What are the options for communication between a SIMOVERT and a PROFIBUS DP master?
You have the following options for connecting a SIMOVERT as PROFIBUS DP slave to a PROFIBUS DP master:
1. Interfacing the slave to the integrated DP connection of an S7-300 CPU
When configuring your SIMOVERT slave in the HW Config you are requested to make a choice regarding the setpoint configuration. If you decide for the PPO type 5, then you have the choice between:
"PPO 5: 4 PKW | 4 + 4 + 2 PZD"
"PPO 5: 4 PKW | 10 PZD".
In both case the sum of all parameter and process data words is identical. There is however a difference in the communication process due to the different distribution of the consistent data areas.
If you select the configuration "PPO 5: 4 PKW | 4 + 4 + 2 PZD", then you must program the communication via three calls of the SFC 15 (DPWR_DAT) and SFC 14 (DPRD_DAT). You always use the SFC 15 and SFC14 when your data length is either 3 bytes exactly or greater than 4 bytes. Since in this case three data blocks of 8 bytes each and one data block of 4 bytes have been selected, it is necessary to have the three SFC calls. The fourth data block is 4 bytes long and can therefore be read directly.
Note: the format of the data length in the HW Config is of the "WORD" type.
If you select the configuration "PPO 5: 4 PKW | 10 PZD", then you only need two calls each of the SFC 15 (DPWR_DAT) and the SFC 14 (DPRD_DAT). One call for the parameter data block (PKW) and one for the process data block (PZD).
2. Using the CP342-5 as DP master
If you use the CP342-5 as DP master, it doesn't matter which setpoint configuration you choose. You can only use the functions FC1 (DP_SEND) and FC2 (DP_RECV). The system functions SFC14 and SFC15 are not available to you in this case.
Note: if you configure a SIMOVERT CBP together with a CP342-5, then the data block is two bytes longer than predefined in the HW Config (PKW+PZD). These two extra bytes are needed for diagnostics.