General Explanation: Data Logger can connect more than one PLCs via distinct serial ports. No limitation for connection number. Connected PLC's tag values reads and writes at the same time without certain order. Thus increase in the number of PLC's does not effects speed of reading data. Other advantage is that you don't need to connect PLCs to the same network in order to reach all PLCs with single Data Logger . The serial port based S7 Adapter USB Adapter you can use. Used for this type of PLC adapter PlcVcom software ver.2.68 should be minimum.
Connect: You can activate only this network.
Disconnect: You can stop only this network. If all networks activated via Data Logger connect button Data Logger restarts this network automaticaly too.
StatusStrip: Information group at the ActiveX subsection. The first data in this group is Tag count. Then "Good" successful communication count. "Bad" is the failed communication count.
Query Byte Count: Most important information for this section. According to entered variable address informations ActiveX automaticaly calculates PPI query and sends to the PLC. Here according to result of the query you can see the byte count that PLC should send. High number means less packet count. Packet number is more important than packet size for the PPI protocol. To improve performance it is necessary to keep down the number of packages.
Ppi Network Menu: PPI Network is the first element of this treeview menu. Second element is station, last element is the group. When element selected tag list at the right filled with that element's tags.
Ppi Network: You can see PC port settings and PPI .NET settings here. When you right click on this area the operation menu opens. Most important parameter of PPI network settings is the pool.interval parameter. By this parameter you can set the period of the queries that sent to the PLC. This has no effect when data written to the PLC. When write command taken data transfers to the PLC without delay.
Station: Station(PLC PPI) address must entered to this area.
Group: One of the most important matters in ActiveX.All serial communication methods have limited capacity. Different groups can be created in order to use this capacity with best way. With groups "cycle" parameter some groups can be read at every cycle some groups can be read less frequently. Thus some PLC values can be read fast some values can be read slow. Applicable number of groups is 128. Other benefit of the groups is the asists arranging query byte number which will detaily explained later. Moreover, it is useful in tracking the data when communicating a lot of data.
Tag List: Table for creating a new tag, monitoring tag's values and writing new values. Group must be selected at the left side in order to make operation on this table. If group is not selected only set value can be write. When group selected only the tags that belong to that group are listed. When station or network selected all relevant tags are listed.
Adress: You need to write Tag's address inside the PLC this column. You can read and write I, Q, M, V, S, SM, T, C, AI, AQ variables with Activex. Adress data specifies data size also. For example M 0.0 is one bit data.Md 8 is 4 byte data. Applicable value types specified by the address written here.
Tag Name: System gives the unused name to added tag. You can change it later then. All tag names must be unique.
Value Type: Siemens S7 PLC's data types are selected at this column. All options here read and transferred to PLC with S7 format. Presentation is made with Windows standart. Shown number types are:Boolean, Usigned int8, Signed int8, Usigned int16, Signed int16, Usigned int32, Signed int32, Floatpoint, Bcd.
Read Value: The values that read from PLC shown at this column.
Write Value: The value written on this column is checked if has error first. If it has not error sent to the PLC. Data input process to the PLC is a priority. As soon as after the active query completed write operation activated without waiting other operations.
To obtain the best performance issues must be considered: ActiveX tries to read all tags within the same group once. Calculates the query that will be sent according to the address data entered to the Tag list. If entered adress are consecutive reads all list at once.Number of bytes to be read at one time is limited to 32. ActiveX reports calculated query size with "Query byte count" which resides Statusstrip. If you see different number than your calculated query size probably you made a mistake.
Let's explain the subject with a couple example. Some query examples and total byte sizes are given below.