Rockwell Automation 1756-DHRIO_DHRIOXT ControlLogix Data Highway Plus-Remote I/O Communication Interface Module - Manual (Page 145)

Rockwell Automation Publication 1756-UM514C-EN-P - June 2014 145
Chapter
12
Block Transfers with the 1756-DHRIO or
1756-DHRIOXT Module
What This Chapter Contains This chapter describes how to use the 1756-DHRIO or 1756-DHRIOXT
module to connect a ControlLogix controller to a remote I/O Block Transfer
(BT) module.
The 1756-DHRIO and 1756-DHRIOXT modules support sending block
transfer (BT) data and discrete I/O 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 (that is 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
requiring instructions.
The process for completing block transfers on remote I/O remains consistent
with all adapters products. 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 or 1756-DHRIOXT module and the
ControlLogix controller. The primary timeout for the BT response is remote I/O
network based. This timeout occurs in 4 seconds if the I/O module fails to
respond to the BT message.
Topic Page
Block Transfers to Remote FLEX I/O Modules through a 1756-
DHRIO or 1756-DHRIOXT Module in a Local Chassis 147
Block Transfers to Remote 1771-ASB I/O Modules through a
1756-DHRIO or 1756-DHRIOXT Module in a Remote Chassis 150