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Chapter 1. Introduction
Overview
This chapter introduces the 3708, describes its components and functions, and
explains host and ASCII device attachment.
The 3708 provides a physical and logical interface for connecting ASCII end-user
devices to an SNA network.
It
has 10 communication ports that can be defined for
various network configurations and operating modes. The network can contain
ASCII hosts, which include personal computers, as well as SNA hosts.
The 3708 accommodates a large range of ASCII devices, including devices that
support ANSI X3.64, and allows attachment to both SNA and ASCII hosts.
It
allows an ASCII device to communicate with a host by providing three modes of
operation, which the 3708 can perform simultaneously, for different network
configurations:
• 3270 applications running on an SNA host. The 3708 provides protocol conversion
mode for communication between an ASCII end-user device and 3270
applications running on an SNA host. This mode changes a start-stop data
stream from an ASCII device into a 3270 data stream and provides 3274 Control
Unit functions, including 3270 full-screen support.
• Line-by-line applications running on an SNA host. The 3708 provides protocol
enveloping mode for communication between an ASCII end-user device and line
oriented applications running on an SNA host. In this mode, the 3708
surrounds the data stream from an ASCII device with SNA headers. Devices
that normally communicate with host applications through start-stop support of
the Network Terminal Option (NTO) can communicate through the 3708. NTO
start-stop support is not required for 3708 operations and can be eliminated
from the communication controller.
• Applications running on an ASCII host. The 3708 provides ASCII pass-through
mode for communication between an ASCII display and applications running on
an ASCII host. This mode passes a start-stop data stream between an ASCII
display and an ASCII host without changing the data stream in any way.
Note: Throughout this book, the term ASCII devices is used to refer to end-user
devices that use asynchronous and start-stop data transmission. These devices
include displays, printers, keyboard printers, keyboard displays with attached
printers, plotters, personal computers, and devices that use ANSI X3.64.
The 3708 is small, lightweight, and portable.
It
is made of two modular,
customer-replaceable hardware components: a base and a cartridge. The cartridge is
inserted into the front of the base. Ten ports for attaching hosts and ASCII devices
are on the back of the 3708. The 3708 measures 400 mm by 355 rom by 105 rom
(15.7 in. by 13.9 in. by 3.9 in.) and weighs about 5.6 kg (12
1/2Ib).
Chapter 1. Introduction
1-1
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