HP Data Entry and Forms Management System (VPLUS) Reference Manual (32209-90024)

664 AppendixL

A Programmer’s Guide to VPLUS

VPLUS & Multiplexers

Using VPLUS on a Pad-Terminal(Connected to a Cluster Controller

HP 2334A)

What is a CLUSTER CONTROLLER?

When you use a Packet Switching Network (PSN) for data communication, you need

equipment to do the packing and unpacking of the data at both ends. A CLUSTER

normally will receive the packets for different users, unpack them and change the

transmission mode from synchronous to asynchronous. This way you can connect several

different asynchronous devices, such as printers and terminals to one X.25 packet line (on

a HP 2334A up to 16).

At the computer side you can use another CLUSTER and connect the asynchronous ports

to the ATP or ADCC ports of the HP 3000. This kind of connection is called STATISTICAL

MULTIPLEXER.

Figure L-1. Statistical Multiplexer

The other way is to connect the X.25 packet line directly to an INP-card in the HP 3000

computer. To support the INP, you need special DS- or NS-software. The software and the

INP-card will do the packing and unpacking of the data received. This conﬁguration is the

CLUSTER CONNECTION and we call it Packet Assembler / Dissassembler (PAD).

Figure L-2. PAD or CLUSTER Connection to an HP 3000 with an INP

Terminal 2334 2334 HP 3000

Term

X.25

Terminal 2334 HP 3000

Term

X.25

I .

N .

P .