Pro I: Signal Conditioning and Interface Modules
Pro-Fieldbus Modules
ADwin
178
ADwin-Pro
Hardware, manual version 2.9, June 2006
Data exchange by handshake
When the DP-RAM is accessed it must be assured that only one side has
access to the memory. In order to ensure that this happens, there is a hand-
shake process between the two sides fieldbus and program.
There is a separate handshake each for the input, out-
put and control areas. Therefore, both sides may have
access to the memory simultaneously, without dis-
abling access for the other side.
After initializing the module and starting of the cyclic
data transfer of the fieldbus, first the bus side has the
right to access the DP-RAM.
The data, sent by the fieldbus master to the
ADwin
system (slave in the bus), is transferred by the fieldbus
and is received and processed by the bus-specific
electronic equipment of the
ADwin
module. The active
data is written into the output area of the DP-RAM.
The program accesses the DP-RAM or parts of it at any
time, (see figure at right). As soon as the fieldbus per-
mits the access, the user reads out the active data from
the output area of the DP-RAM and writes data into the
input area of the DP-RAM.
As long as the user side has the access right, the field-
bus cannot access the DP-RAM. The Pro module con-
tinues to execute its tasks as fieldbus slave, that is the
slave meets all requirements of the bus master. Data
arriving from the fieldbus is buffered in the bus-specific
electronic equipment of the module.
If the user has exchanged all data with the DP-RAM, he
has to return the access right to the bus side. Now the
electronic equipment of the module writes the buffered
data into the output area of the DP-RAM and gets data
from the input area of the DP-RAM. At the next bus
cycle the bus master gets the input data and writes
data into the output area.
explains the data flow in the fieldbus module.
Fig. 309 – Pro-Fieldbus-SL: Data flow in the module
Start
Request
access right
Access
permitted
No
Read from output
area
Write to input
area
Yes
Return
access right
End
ADwin-
P
ro
-Bu
s
Fie
ld-Bus
Dual-
Port-
RAM
Glue-
Logic
Bus-
Controller
(µC)
