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2408
f
& 2404
f
PROFIBUS Communications Handbook Demand Data
2408
f
and 2404
f
PROFIBUS Communications Handbook 7-5
Worked example 2 - Uploading Program Data
The 2400
f
series with PROFIBUS-DP may be configured with a ramp/dwell programmer option. It is often the case that
specific ramp dwell sequences need to be downloaded to an instrument. Because of the amount of data involved, it would be
impossible if only standard PROFIBUS-DP input and output frames were to be used. Use of the demand data protocol is the
only way the operation may be performed.
Note that if the programmer option is configured, the instrument defines two types of program data store. Program 0 holds a
copy of the currently running program (if any) which may be accessed or changed in ‘hold’ mode only. Programs 1, and 2, 3,
and 4 for a 4 programmer instrument, hold the actual program data and may be accessed at any time.
From the tag list, we find that the Program 1 has tags running from 8328 to 8463. This is above the maximum of 2047 for a
standard tag read, so we will need to use the Eurotherm extensions.
Note that a program download is essentially the inverse of this operation, using extended tag writes.
The sequence of operations to upload a ramp/dwell program is as follows:
Request 1: Clear any previous demand data requests. You should do this at the start of any sequence of operations using
demand data in order to ensure that the system is properly initialised.
PLC Output Register Number Output Data Comment
10
2 Anything
3 Anything
4 Anything
Response 1 Wait until the following response message is received in the input data:
PLC Input Register Number Input Data Comment
10
2 Anything
3 Anything
4 Anything
Request 2: Read from the first program address.
PLC Output Register Number Output Data Comment
1 12288 Extended read tag 3000 (Hex)
2 8328 Program 1 tag address,. see Chapter 8
3 Anything
4 Anything
Response 2: Wait for one of the following responses to be received.
a. An error has occurred
PLC Input Register Number Input Data Comment
1 37000 Error 7000 (Hex) (28672 dec) + tag address 8328 (dec) = 37000
2 Anything
3 Anything
40
1
2
Invalid tag number
Read only parameter
Value out of range
b. No error.
PLC Input Register Number Input Data Comment
1 12288 Extended read tag 3000 (Hex)
2 8328 Program 1 tag address,. see Chapter 8
3 Anything
4 Anything
If there was no error, store the Program Value in the required memory location, increment register 2 in the request message,
and repeat until tag 8463 (end of program 1 segments) has been reached.
Tags
Parameter Tags may be obtained by reference to the following chapter. Note also that the GSD Configuration Program allows
the display of the tag for a given parameter, by clicking the right mouse button when pointing to the parameter.