Low-Speed Scanner (LSS)
Definition
A low-speed scanner (LSS) is located on a communication scanner card (CSC) consisting of:
A communication scanner processor (CSP)
A front-end scanner low-speed (FESL).
CSC
┌─────────────────────────────────────────┐
│
┌─────────────┐
┌─────────────┐
│
IOC bus │
│
│
│
FESL
│
│
Serial link
────────┼──┤
CSP
├───────┤
├──┼─────────────
│
│
│
│ FES
FESA │
│
│
└─────────────┘
└─────────────┘
│
└─────────────────────────────────────────┘
Communication Scanner Processor (CSP)
The communication scanner processor (CSP):
Supports various line protocols with partial handling of the data link control for BSC and SDLC lines.
(The microcode allows the implementation of specific customer protocols.)
Provides character buffering and cycle steal transfer into CCU main storage
Supports start-stop with: 8/5, 9/7, 10/7, 10/8, 11/8 bits, BSC (EBCDIC, ASCII), SDLC, DIAL, X.21
native and X.21 bis
Controls transmission interfaces
Handles a variable number of lines depending on the protocol and transmission speed
Provides four types of operating mode with NCP/EP
Performs the checkout of the ROS code
Interconnects the IOC buses through the receivers and drivers.
Front-End Scanner Low-Speed (FESL)
The front-end scanner low-speed (FESL) provides logical connection between the CSP and the LIC unit.
It is composed of:
The front-end scanner (FES)
The front-end scanner adapter (FESA).
FES: It is composed of two layers:
The front-end layer serializes and deserializes the characters, provides line service management
depending on the protocols and exchanges the characters with the scanner processor.
The scanner base layer communicates with the CSP via several paths:
– An asynchronous path is used by the CSP microcode to initialize and send commands to the
FESL and the LICs.
– A cycle steal path supports data exchange of one halfword with the CSP control store.
An interrupt mechanism is used to request line service management.
FESA: The FESA converts FES parallel data into a serialized bit stream and conversely to communicate
with the LIC units. In addition, the FESA performs modem-in control lead confirmation.
LIC Board
Chapter 4. Transmission Subsystem (TSS)
4-7
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