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Range 2
Range 3
Message block
number
Buffer overflow
SIPROTEC PROFIBUS-DP - Communication profile
C53000-L1840-B001-03
This range of the input telegram contains measured values, metered values etc.
The information contained in this range is not part of the event list.
Single-point and double-point indications that are to be transmitted only within the
cyclic telegram image can also be allocated in this range, depending on the mapping
file that is available.
Handshake byte and message blocks for retrieval of the event list
In Figure 2-3 the meaning of the individual bits of the handshake byte "Control_l" are
represented.
Handshake mechanisms are referred to in chapter 2.5.3.
7
6
5
Message block
number
Figure 2-3 Handshake byte "Control_I" (input direction)
• With each transmission of the message blocks (entries from the event list, max. 3
entries per telegram), the message block number is increased sequentially by 1,
starting with 1 (0001
• The message block number only has the (initial) value 0 if, following the initial or
reboot of the SIPROTEC device no entries are available in the event list yet.
After transmission of the first entry in the event list and the associated increment of
the message block number, this number never assumes the value 0 again (unless
another initial or reboot takes place).
• If the telegram contains none or less than 3 entries in the event list, then the unused
message blocks are completely filled up with zeros.
• If no annunciation changes were transmitted in the event list during a number of bus
cycles then the message block number remains unchanged in its value during this
time.
The same last transmitted message block number is transferred repeatedly until
new entries in the event list also effect changes to the message blocks that are
transferred, thereby incrementing the message block number.
At the same time, the value of the message block number provides the acknowledge-
ment that the message block entries were received by the PROFIBUS-DP master via
the handshake byte in the output telegram (ref. to chap. 2.5.2.2)
A set bit indicates an overflow of the event list buffer.
The buffer overflow bit is reset following acknowledgement of the current transmitted
message blocks if no new buffer overflow occurred in the meantime.
Control_I
4
3
2
1
reserved = 0
) up to 15 (1111
), and thereafter starting with 1 again.
bin
bin
Parameters and properties
0
Bit position
Meaning
41
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