Yaskawa JAPMC-MC2303-E - Manual (Page 76)

5
Details of FL-net
5.3 FL-net Data Communication
5.3.1 Cyclic Transmission
5-9
5.3 FL-net Data Communication
The following describes data communication, cyclic transmission, and message transmission supported by FL-net in
detail.
5.3.1 Cyclic Transmission
( 1 ) Overview of Cyclic Transmission
Cyclic transmission is a function for cyclic data exchange between nodes.
• The common memory function for each node is realized.
• When the node holds a token, cyclic data to be sent is all sent.
• Nodes not performing cyclic transmission (nodes performing only message transmission) are allowed to join FL-
net.
( 2 ) Token and Token Frame
Basically, only one token is present in a network. When the network contains two or more tokens, the node preferen-
tially selects the token with a smaller destination node number and discards the others.
A frame including a token (token frame) has a token destination node number and a token source node number. When
the node number of a node matches the destination node number of a token in a received token frame, the node changes
to a token holder node.
The order of token rotation is determined by the node number. Each node passes the token in the ascending order of
node numbers registered in the joined node management table. A node having the maximum node number passes the
token to a node having the minimum node number.
( 3 ) Refresh Cycle and Refresh Cycle Allowable Time
Cyclic communication refreshes (updates) the common memory at a constant cycle. This update cycle is called a
“refresh cycle.”
FL-net controls the sending of message communication so that the common memory refresh cycle does not exceed the
refresh cycle allowable time during a single message communication.
Each node monitors the message communication frame that flows through the network from when the node receives a
token addressed to itself until it receives another token addressed to itself. When no message communication frame
flows in this specific cycle, a 120% value of this one cycle time is set as the refresh cycle allowable time.
The refresh cycle allowable time is determined automatically by the number of nodes to join the network through the
above monitoring.
( 4 ) Common Memory and Areas 1 and 2
The common memory can be shared among nodes for cyclic transmission.
A node can assign two data areas (called “area 1” and “area 2”) to the common memory. To define a send area, the
leading address and size of an area must be specified.
Area access is performed in units of words. The size of area 1 is 0.5 kword (8 kbits) and that of area 2 is 8 kwords. Each
node can define a node send area freely within the maximum area size of area 1 or area 2.
ΠFor details of common memory assignment, refer to 5.3.1 ( 5 ) Assignment of I/O Register and Common Memory on
page 5-10.