Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 20)

1–3 Network Layers
Publication 1770Ć6.5.16 - October 1996
DH Link
A DH link is a local area network (LAN) designed for factory-floor
applications. This link accepts 64 devices and can transmit 57.6 K
bits of data per second.
A DH link consists of a trunk cable up to 10,000 feet (3,048 meters)
long and drop cables as long as 100 feet (30.48 meters) each.
Each node is at the end of a drop cable and connects to the DH link
through a station connector (cat. no. 1770-SC). This is the only
configuration tested and supported by Allen-Bradley.
This processor Connects to a DH link through the
PLCĆ2 family
DH PLCĆ2 family communication adapter module
(cat. nos. 1771ĆKA2, ĆKG)
PLCĆ3
DH PLCĆ3 family communication adapter module
(cat. nos. 1775ĆKA,ĆS5, ĆSR5)
PLCĆ5/250
Resource manager module
(cat. nos. 5130ĆĆKA, ĆRM1,ĆRM2)
PLCĆ5, SLC 5/04 ➀
DH+/DH communication module
(cat. no. 1785ĆKA)
➀ Although a PLCĆ5 processor does not directly connect to a DH link, it can communicate with
devices on a DH link via the 1785ĆKA module.
A DH link implements peer-to-peer communication through a
scheme called the floating master. With this arrangement, each
node has equal access to become the master. The nodes bid for
temporary mastership based on their need to send information.