Rockwell Automation Allen-Bradley SynchLink 1756-DM Series Design Manual page 19

Buffered data must be copied from the
receive port to the transmit port (via host
controller intervention) before it can be
transferred to the next SynchLink node.
In this graphic, the following events occur:
1. The 1756-L55 controller in chassis
A produces axis data.
2. The 1756-SYNCH module in
chassis A consumes the axis data
from the backplane and produces it
on SynchLink.
3. The 1756-SYNCH modules in
chassis B & C consume the axis
data from SynchLink and produce it
on their local backplanes.
4. The 1756-L55 controllers in
chassis B & C consume the axis
data from the backplane and use it
in their motion planners.
· Buffered - Data that exceeds the four-word limit of a direct data
transfer. Buffered data is appropriately segmented at the
transmitting device and reassembled at the receiving device.
Buffered data cannot be automatically forwarded to the next
SynchLink node in the daisy chain or ring configurations. In this
case, transferring buffered data to the next node requires
intervention by the host controller, as shown below.
SynchLink Node
Buffered
input data
storage
Receive
· Axis data - Motion data used by the motion planner in the
controller. Only the 1756-SYNCH module can
produce/consume Axis data to/from its local controller, as
shown below.
1756-L55 controller
SynchLink
1756-SYNCH 1756-MO2AE
1756-L55
controller
Chassis B
Axis data is not automatically forwarded to the next SynchLink
node in daisy chain or ring configurations. The data transfer
requires host controller intervention similar to that shown above
because axis data is a specific form of buffered data.
Host
controller
Buffered
output data
storage
SynchLink
Transmit
1756-SYNCH 1756-MO2AE
Chassis A
1756-L55
controller
Chassis C
Publication 1756-TD008A-EN-P - August 2002
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ControlNet
1756-SYNCH
1756-M08SE
1-7
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