S7-200 Addressing

The S7-200 addressing format is the same as the S7-200 PPM addressing format. The model selection in this case determines whether the driver is using PPI protocol (normal S7-200 Mode) or PPM (S7-200 in Point to Point Modem) mode. In both cases, the addressing is the same.

 

The default data types for dynamically defined tags are shown in bold.

 

 

*For Timer and Counter status bits, dot bit notation is not used. The status bit for timer 7 would be T7 declared as Boolean.

 

**For Analog Inputs and Outputs, the address must be even (AI0, AI2, AI4...). Analog Outputs (AQ) are Write Only: there is no method for reading the value of Analog Outputs from the device. Write-only data types of this driver return the last value written when read if an initial write to device has completed. If an initial write has not completed, the driver returns a value of 0 when read. This only applies while a client is connected to the server.

 

The actual number of addresses of each type depends on the Siemens S7-200 device in use. Each type does not necessarily support an address of 0 to 65535. For address ranges, refer to the device's documentation.

 

Optional Dot Bits

For Byte, Word, Short, DWord or Long data types, an optional .bb (dot bit) can be appended to the address to reference a bit in a particular value. The valid ranges for the optional bit is 0-7 for Byte types; 0-15 for Word, Short, and Boolean types; 0-31 for DWord and Long types; and 1-211 for String types. Float types do not support bit operations. Boolean and String types require a bit number. The bit number for String types specifies the number of characters in the string.

 

Dynamic addresses with bit numbers in the range of 0-7 default to Byte; 8-15 default to Word; 16-31 defaults to DWord. V Memory addresses with a bit number larger than 31 defaults to String. The following diagram illustrates how the driver maps bits within the controller.

 

 

 

Arrays

Certain memory types (I, Q, M, SM, V, AI, and AQ) support an array operation. Boolean arrays are not allowed at this time. To specify an array address, append [rows][cols] to the end of an address. If only [cols] is specified, [rows] defaults to 1. With the array type, it is possible to read and write a block of 200 bytes at one time.

 

The maximum array size for Word and Short types is 100, and for DWord, Long and Float types is 50. The array size is determined by the multiplication of rows and cols.

 

 

Examples

1. To read and write an array of 10 Variable Memory Float values starting with V10, declare an address as follows: V10 [1][10]. Choose Float for the data type.

 

 

2. To read and write to bit 23 of Internal Memory Long M20, declare an address as follows: M20.23. Choose Long for the data type.

 

Strings

The driver allows for variable length strings to be stored in Variable Memory locations. The bit number specifies the string length (1-211) in characters. String data that is sent to the device, but is smaller in length than the string character count (bit number), is null terminated. String data that meets or exceeds the character length is truncated to the character count and sent to the device without a null terminator.

 

To read and write a string starting at V5 for a length of 10 characters, declare an address as follows: V5.10. Choose string for the data type.