Page 53 of 82
Date: 27.01.06
•
Meas. toggle count
•
These bits indicate when a new measured value has been recorded.
•
It is a 4-bit counter, which is incremented every time a new
measurement reading is made.
•
Depending on the PROFIBUS cycle time and the averaging period, it
may not be possible for every single measurement to be retrieved by
the PROFIBUS. If the cycle time is relatively large and only a relatively
few values are averaged, then viewed from the PROFIBUS master, the
counter will appear to jump in value
(e.g. 1-5-9-c-2-6-a-....).
•
Mirror of the two control bytes
•
Control signals are classified as
action-
oriented
and
state-oriented
.
•
Action-oriented:
A positive edge on the control line concerned is intended to start an
action (e.g. tare). Once the action has been started, the control line can
return to its initial state. The following handshake procedure is followed
to monitor this action.
The relevant bits in bytes 3 and 4 have been labeled with “Handshake”.
•
State-oriented:
In this case the current state of the setting concerned is constantly
output. No additional handshake is required.
1
0
Control bit
from master
Master wants
to initiate
action
1
0
Handshake
from 9221
9221 signals
that action has
been performed
Master has detected
acknowledgment and wants
to terminate handshake
9221 confirms the end of the
handshake and is thereby
ready for the next action on this
channel
