INFICON BCG450-SP ATM to Ultra-High Vacuum Triple Gauge (Profibus) - Manual (Page 10)

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tira41e1 (2005-06) BCG450SPv1.cp
1) The master transmits an instruction to the slave and repeats that instruction
until it receives a response from the slave.
2) The slave keeps transmitting the response to the instruction until the master
transmits a new instruction.
3) The master marks the end of the first instruction cycle by setting AK to zero.
Only after that, a new instruction/response cycle may be started.
The PWE represents the data element to be transmitted.
If a byte is to be transmitted, that byte has to be in position 8 of the parameter
channel.
Integers are transmitted with bytes 7 and 8. Double integer and float values are
transmitted with bytes 5 … 8.
In the event of a transmission error (AK response signature = 7), the slave trans-
mits an error code in byte positions 7 and 8 (data type: INT16).
Error code Meaning
0 Undefined slot
1 Parameter not changeable
2 Lower or upper value range limit overflow
3 Index error
5 Data type error
17 Instruction not allowed in this state
18 Other errors
201 Already in requested state
202 Object state conflict
The following diagram shows an example of a data request from a master to a
BCG450-SP via parameter channel.
AK(RS) = 0
BCG450-SP DP-Master
AK(RS) = 0
AK (IS) = 1
AK(RS) = 1
AK (IS) = 1
Parameter
Request
(Client)
AK(RS) = 0
AK (IS) = 1
AK(RS) = 0
AK (IS) = 0
AK(RS) = 0
Store
Data
AK (IS) = 0
AK(RS) = 0
Parameter
Request
(Server)
AK(IS) = 0
AK(IS) = 0
Fetch
Data
Instruction – response
sequence
2.2.1.2 PWE Parameter
(Process Value)
2.2.1.3 Error Code
(Error Message)