Installation guide

76 Estimating Network Performance
890 USE 100 00
3.9 Reading and W riting Global Data
3.9.1 Passing Global Data Between Nodes
Up to 32 registers of global data can be included in the network token
frame as it is passed between nodes. In the node currently holding the
token, an MSTR function can be programmed to include global data in
the next token pass. The global data will be read into the peer
processors of the other nodes on the same network, and will update the
storage area in those nodes. Global data is not passed through bridges
from one network to the next.
The application program in each node can have an MSTR programmed
to read all or a certain portion of the global data. Nodes accept global
data without waiting for paths or queueing.
Figure 34 shows a sample global database pass.
CONTROLLER
A
PEER
PROCESSOR
CONTROLLER
B . . . n
PEER
PROCESSOR
MODBUS PLUS NETWORK
TOKEN PASS >
ALL OTHER NODES
CAN ACCESS DATA
IN THE TOKEN FRAME
ON THIS NETWORK
Figure 34 Sample Global Database Pass
During the ladder logic scan in unit A, an MSTR block is enabled that
specifies a Write Global Database operation. At the end of the block
execution, the global data is sent to the peer processor in unit A. The
following events occur: