Leroy-Somer digitax st User Manual page 36

TELEGRAM 2
The second telegram from the PROFIBUS-DP master also indicates a READ cycle, but
the stamp number is now 2. The data byte would contain the parameter number for the
parameter that is to be read.
Example telegram
Bit
Value
Data word = 0x9201
Stamp number = 2
Parameter = 1
When the second telegram has been received and processed in the slave, it is mirrored
in the non-cyclic IN word. This is the signal to the master controller program that the
second telegram of the message has been received and the third telegram can now be
transmitted.
If telegrams 1 and 2 were not received correctly or an invalid parameter was specified,
NOTE
(e.g. parameter is write only, or does not exist), the PROFIBUS-DP interface will set the
ERROR bit to 1 (b14 = 1) in the response. The data bits will have no significance.
Setting the stamp number to 0 resets the internal non-cyclic state machine.
Example response
Bit
Value
Data word = 0x9201
Stamp number = 2
If an error is reported, the non-cyclic data word should be set to 0 to ensure that the
NOTE
non-cyclic state machine is completely reset and ready for the next non-cyclic READ or
WRITE sequence.
TELEGRAM 3
The third telegram from the PROFIBUS-DP master acts as the indication to the slave to
send the high data byte from the requested parameter. The data byte is not used in this
telegram, and should be set to 0.
Example telegram
Bit
Value
Data word = 0x9300
Stamp number = 3
When the third telegram has been received and processed in the slave node, the node
will mirror the stamp number in the non-cyclic IN word and load the high byte of the
parameter value into the data byte.
Example response
Bit
Value
Data word = 0x9300
Stamp number = 3
Data high byte = 0x00 = 0
36
b15-b12 b11-b8
1001 0010
b15-b12 b11-b8
1001 0010
b15-b12 b11-b8
1001 0011
b15-b12 b11-b8
1001 0011
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b7-b4 b3-b0
0000 0001
b7-b4 b3-b0
0000 0001
b7-b4 b3-b0
0000 0000
b7-b4 b3-b0
0000 0000
SM-PROFIBUS DP-V1 User Guide
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