1 Publication 1756-UM514B-EN-P - February 2003
Chapter
11
Block Transfers with the 1756-DHRIO Module
What This Chapter Contains
This chapter describes how to use the 1756-DHRIO module to
connect a ControlLogix controller to a remote I/O Block Transfer (BT)
module.
In addition to discrete I/O, the 1756-DHRIO module supports sending
block transfer (BT) data to the ControlLogix controller. This data
exchange transfers up to 64 words of data to/from a selected I/O
module.
The BT data exchange is message-based (i.e. a message instruction in
the Ladder Logic program of the ControlLogix controller must be used
to initiate the BT request). In the case of digital I/O modules, simply
by entering the adapter in the ControlLogix controller organizer, data
is transferred without specific instructions required.
The process for completing block transfers on remote I/O remains
consistent with all adapters products. All the remote I/O network
characteristics defined for the PLC-5 remote I/O scanner are the same
for the 1756-DHRIO remote I/O scanner.
Block Transfer Fault
Notification
The message timeout for the BT message is fixed at 4.5 seconds. This
timeout is a ControlLogix network response timeout associated with
the connection established between the 1756-DHRIO module and the
ControlLogix controller. There is a primary timeout for the BT
response that is remote I/O network based. This timeout occurs in 4
seconds if the I/O module fails to respond to the BT message.
For information about using See page
Block Transfers to Remote FLEX I/O Modules
Through a 1756-DHRIO in a Local Chassis
11-3
Block Transfers to Remote 1771-ASB I/O
Modules Through a 1756-DHRIO in a Remote
Chassis
11-7
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