User manual

Computer Gateway User Manual 1-1 5/96
1
INTRODUCTION
Section 1
This section discusses the CG role in a TDC 3000
X
System; reviews the most significant hardware
and software components of the CG; and lists the other publications you need to consult during
implementation and operation of a host computer-to-CG data link.
1.1 COMPUTER GATEWAY ROLE IN TDC 3000
X
SYSTEMS
Figure 1-1 shows an overview of the TDC 3000
X
System architecture. The Computer
Gateway is a fully integrated node of that system, enabling it to exchange information with
all other nodes on the same LCN. Its function is to serve as a communication link between
your host computer and the LCN, making data exchanges with the host computer appear
identical to those with any other LCN node. These characteristics provide the foundation
for a broad range of potential applications for the host computer.
1.2 CG ARCHITECTURE
The Computer Gateway is a standard LCN node. Its hardware components include an
LCN interface, MCPU, memory, a power supply, and a Communications Line Interface
(CLI) board with an RS-232C compatible or RS-422 compatible data link. An enhanced
version of the CG called a Plant Network Module (PLNM) replaces the CLI board with a
Computer Network Interface (CNI) board that enables it to communicate with nodes on a
DECnet network. The CG memory contains the standard TDC 3000
X
node environment
software along with CG-specific application software and a user-defined database. Its
relationships to the Host Processor and to the LCN are shown in Figure 1-2.
1.3 CG PREPARATION
The Computer Gateway is prepared for its role through the system-configuration process,
much like any other LCN-resident node. During configuration, the process engineer
informs the system that the CG exists, and what options (such as data link type) are
selected, then initiates its loading. Then comes point configuration of ACIDP and CRDP
data points and their custom data segments.
Final CG preparation, such as the connection of host-processor-resident programs to
ACIDPs for scheduling, and the creation of data-point-specific Internal Data Definition
Tables are handled through a series of messages initiated by the host processor.
1.4 HOST PREPARATION
The host computer must have the hardware and software to support your choice of either
Bisynch or HDLC communications over RS-232C or RS-442 circuits. Additional software
is required to support the communications-message structure defined in this document and
the specifics of your desired application.