Rockwell Automation 1756-SYNCH ControlLogix SynchLink Module User Manual - Manual (Page 34)

Publication 1756-UM521C-EN-P - July 2004
3-6 SynchLink Module Features
transferred between them). The SynchLink module can receive and
transmit data and, therefore, uses a Receive Port Communications
Format and Transmit Port Communications Format.
SynchLink messages are structured as six 32-bit words; the words are
divided into three types as described in Table 3.3:
The Communications Formats available on the 1756-SYNCH module
use various combinations of the words described in Table 3.3. The following
choices are available:
• 1 Axis, 3 Direct Words, 14 Buffered
• 2 Axis
• 2 Axis, 3 Direct Words
• 2 Direct Words, 18 Buffered
• 4 Direct Words, 18 Buffered
• 4 Direct Words, 8 Buffered
• No Receive Data - Available on the Receive Port only
• Listen Only, No Transmit Data - Available on the Transmit
Port only
• No Transmit Data - Available on the Transmit Port only
Table 3.3
Word Type: Description:
Direct Data delivered in a single message. A SynchLink message can contain
a maximum of four direct data words; each word is 32 bits in length.
Direct data can be automatically forwarded to the next node in the
daisy chain and ring configurations.
Buffered Data that exceeds the four word limit of a direct data transfer.
Buffered data is appropriately segmented at the transmitting module
and reassembled at the receiving module. Buffered data cannot be
automatically forwarded to the next node in the daisy chain and ring
configurations.
Axis data Motion data used by the motion planner in the controller. The
1756-SYNCH module can consume an Axis tag from a controller and
pass it over SynchLink. A controller in another chassis can then
consume axis tags passed over SynchLink from the 1756-SYNCH
module in that chassis. This data is not automatically forwarded in
daisy chain or ring configurations.