The S7 315T 3PN.DP is connected to CU305DP by Profibus DP.

STEP 1 - After a Power ON:

Function FB401 MC_POWER from Technology Pack is used.

Enable = False;

Status = False;

Busy = False;

Error = False;

In servo Enable = FALSE

Step 2 - After FB401 ENABLE= TRUE

ENABLE = TRUE;

STATUS = TRUE;

BUSY = TRUE;

ERROR = FALSE;

In servo = ENABLE = TRUE

STEP 3 : FB401 ENABLE= FALSE (AGAIN)

ENABLE = FALSE;

STATUS = TRUE;

BUSY = TRUE;

ERROR = FALSE;

In servo = ENABLE = TRUE

STEP 4 : FB401 ENABLE= TRUE (AGAIN)

ENABLE = TRUE;

STATUS = TRUE;

BUSY = TRUE;

ERROR = FALSE;

In servo = ENABLE = TRUE

Conclusion :

- I not able to controll the ENABLE/DESABLE DRIVE .

_ The other functions (MOVE_RELATIVE, ETC) don't work

- Reset function work

- In all this time are not error in SERVO DRIVE and in DB Axis : STATUSWORD.CyclicInterface = TRUE

... which Telegramm have you confiugred?
For example S110 doesn`t support telegramm 105 as standard - as I remember.