PKW IN Data
PKW IN data response (LTMT main unit to PROFIBUS DP client) is mapped in modules supporting PKW. The LTMT main unit echoes the same register address and function code or eventually an error code:
|
Word 1 |
Word 2 |
Word 3 |
Word 5 |
||
|---|---|---|---|---|---|
|
Register address |
Toggle bit (bit 15) |
Function bits (bits 8 to 14) |
Not used (bits 0 to 7) |
Data to write |
|
|
Same register number as in request |
Same as request |
ERROR Code 0x4E |
0x00 |
Error code |
|
|
R_REG_16 Code 0x25 |
Data read in register |
– |
|||
|
R_REG_32 Code 0x26 |
Data read in register 1 | Data read in register 2 | |||
|
W_REG_16 Code 0x2A |
– |
– |
|||
|
W_REG_32 Code 0x2B |
– |
– |
|||
Depending on the PLC platform used, refer to the PKW IN description in little and big endian formats to know the positioning of each field inside each word.
If the initiator tries to write a TeSys Tera object or register to an unauthorized value, or tries to access an inaccessible register, an error code is triggered (function code = toggle bit + 0x4E). The exact error code can be found in words 3 and 4. The request is not accepted and the object or register remains at the old value.
If you want to re-trigger exactly the same command, you must:
-
Reset the function code to 0x00.
-
Wait for the response frame with the function code equal to 0x00.
-
Set it again to its previous value.
This is useful for a limited client like an HMI. Another way of re-triggering exactly the same command is to invert the toggle bit in the function code byte.
The response is valid when the toggle bit of the response is equal to the toggle bit written in the answer (this is a more efficient method, however it requires higher programming capabilities).