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CHAPTER 8 – Operation with Profibus
SMT-BD1/t
Bits 0 to 10 include the parameter number (PNU).
Bit 11 indicates an event message: the parameter is both modified and sent by the amplifier.
Bits 12 to 15 include the instruction or reply code.
Reply codes (slave -> master):
Reply code
Function
0 No
function.
1
Value of the transferred parameter (word).
2
Value of the transferred parameter (double word).
7
Instruction cannot be executed (see error code).
8
PKW interface inhibited.
For instructions that cannot be executed, the slave answers with an error number in the 4
th
word of the PKW (bits
7 and 8).
Error number
Description
0 PNU
unlegal.
1
Parameter cannot be changed.
2
Exceeding of lower or upper limit.
3
Index error (2
nd
word of PKW)
5
Incorrect data type
17
Instruction cannot be executed during operation.
18 Other
error
1.3.2 - PARAMETER VALUE (PWE)
PWE includes the data for the parameter to be transferred:
- word: bytes 7 (MSB) and 8 (LSB).
- double word: bytes 5 (MSB) to 8 (LSB).
1.3.3 - RULE OF THE INSTRUCTION/REPLY COMMUNICATION
- The master sends an instruction to the slave with the message "PPO write". It repeats this instruction until it
gets a reply from the slave by "PPO read". This procedure guarantees the instruction/reply communication by
the operator.
- Just one single instruction can be executed at once.
- A slave provides the reply until the master sends a new instruction.
- An instruction (8 bytes) must be completely transferred in a message, and a reply as well.
- If no parameter setting information is required, the master must send 0 in AK (no instruction).
1.4 - Global control
The PROFIBUS DP global control mechanism can be used for synchronizing the outputs and inputs of several
modules and several slaves. There are 4 global controls: SYNC, UNSYNC, FREEZE and UNFREEZE.
When the master sends a global SYNC control, the outputs of the addressed slave are frozen at their current
values. When the master sends the next data, those are stored in the slave and the outputs status remains
unchanged. When the next SYNC control is sent, the stored outputs values are switched through to the outputs.
An UNSYNC control can be used for ending the synchronous mode.
The FREEZE control also allows the slave to freeze the inputs at their current values and to send them with the
next data transfers. The inputs are not updated until the next FREEZE control. The FREEZE mode can be left by
means of an UNFREEZE control.
The SMT-BD1/t amplifier accepts the global controls SYNC, UNSYNC, FREEZE and UNFREEZE.