Write-only block items

The following table summarizes the data format, item or point, suffix, data type, and range for Write-Only Block Items. See Conversions and suffixes of items (absolute addressing) for suffix definitions.

*: For DDE/SuiteLink, the item value is the Hex ASCIi representation of the complete array. The result is one string containing all the elements of the array in the Hex ASCIi representation of the binary data in big-endian format when data is returned to the DDE/SuiteLink layer.

**: The starting address is always at 0 for Writes. The number of bytes written to the PLC block is determined from the length of the input byte stream. However, the length of the byte stream must be less than 65535.

***: The Siemens S7 block write protocol BSEND does not allow a starting address. All block writes to the PLC always start at address 0. To circumvent this limitation, the BWC item syntax allows for a starting address. The logical number of bytes written to the PLC block is determined from the difference in the start address and end address, (q-x+1), or the length of the input byte stream.

If the input byte stream is longer than the (q-x+1), only (q-x+1) bytes are written.

If the input byte stream is shorter than (q-x+1), the whole input byte stream is written.

Internally, the Communication Driver allocates cache buffers based on the PLC data block and the end address. For more information, see Block Write Caching.

****: The BWCd-q.Send item is readable to allow monitoring of the status of the block send function.

Where:

Note: All BW and BWC block items are Write-Only. BWCxx.Send items are Read/Write. The longest string or array that can be written in a block service is the length of 65534 bytes. The longest string the InTouch software can process is 131 bytes.