Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 19)

1–2 Network Layers
Publication 1770Ć6.5.16 - October 1996
The physical layer is a set of cables and interface modules that
provides a channel for communication between the nodes. A node is
a connection point onto a network, typically containing a unique
address.
When you connect a computer serially to your DH, DH+, DH-485,
or ControlNet link, the interface module acts as an interface between
the:
•
DF1 link (RS-232 or RS-422-A)
•
network link (DH, DH+, DH485, ControlNet link)
DF1 Link
A DF1 link provides:
•
master-slave communication through a half-duplex protocol
•
peer-to-peer communication through a full-duplex protocol
This manual provides information necessary to write your own
driver for an intelligent device on a DF1 link. See “Software
Layers,” on page
1–7 , for the layers your software driver must
implement so that your intelligent device can talk to other DH,
DH+, DH485, or ControlNet nodes.
Network Link
These network links are available for peer-to-peer communication:
This link Connects And allows See page
DH
• PLCĆ2  , PLCĆ3 
processors
• color graphic systems
• personal computers
• host computers
• programmable
RS232/RSĆ422 devices
up to 64 nodes ➀ 1-3
DH+
• same devices as DH
• PLCĆ5 processors
• SLC 5/04 processor
up to 64 nodes 1-5
DH485
• SLC 500 processors
• color graphic systems
• personal computers
up to 32 nodes 1-6
ControlNet
• PLCĆ5 processors
• I/O devices
• personal computers
• operator interface devices
up to 99 nodes --------
➀ Using bridges (e.g., 1785ĆKA modules), you can extend the length of your DH network to contain
up to 255 nodes.
Physical Layer
DH/DH+/DH485 link
DF1 link
nodes
IBMĆPC XT, AT or
compatible computer
RSĆ232 Network Interface
network link
ControlNet
link