Asynchronous Terminals and Printer Processes Programming Manual

INTRODUCTION
6100 CSS Architecture
Hardware
| The 6105 CC, 3605 CC, 6106 ACC, and 3606 ACC are single-board
| implementations of the 6100 CSS architecture.
|
| The 6105 CC and 3605 CC have four ports. Data can be transmitted
| and received over the lines attached to these ports using any
| combination of asynchronous, byte-synchronous, or bit-synchronous
| protocols. These controllers use the RS-232C interface to
| transmit and receive electrical signals; they do not support the
| current loop interface.
|
| The 6106 ACC and 3606 ACC have 16 asynchronous ports. Data
| can be transmitted and received over the lines attached to these
| ports using only asynchronous protocol. These controllers use
| both the RS-232C and current loop interfaces to transmit and
| receive electrical signals.
The DPCIU and SPCIU implementations have two programmable I/O
controllers called Communications Interface Units (CIUs). The
CIUs are located in the I/O card cage of the Tandem host.
The CIUs interface to the 6100 subsystem cabinet through dual,
high-speed, full-duplex, serial buses and connect to the Tandem
NonStop processors through I/O channels. Connections to I/O
channels can be in dual-port or single-port configuration. The
subsystem cabinet contains up to 15 Line Interface Units (LIUs),
for a total of 15 to 60 communication lines, depending on whether
they are LIU1s or LIU4s.
The key to the 6100 CSS architecture is the LIU. The LIU is
composed of a Communications Line Interface Processor (CLIP) and
a Line Interface Module (LIM). The CLIP holds the protocol
module that performs physical I/O, controls modem signals,
and handles the device-dependent functions of the terminal
or printer, such as cursor movement and form control. The
LIM provides the electrical and physical interface to the
communication line. RS-232C and current loop interfaces are
available with the 6100 CSS.
In the single-board implementations, the CLIP and the LIM are
located on the controller board. The physical interface is
provided by a patch panel. In the CIU-based implementations, the
CLIP and the LIM are two separate boards that reside in the 6100
CSS cabinet.
Each LIU has at least two paths to the CPU: path A and path B.
This arrangement allows communication to continue after failure
of a processor or I/O channel.
1-4 November 1987