Low-Speed Scanner
A low-speed scanner consists of a communication scanner processor (CSP)
associated to a front-end scanner low-speed (FESL).
Communication Scanner Processor
The 3745 uses a microprocessor-based communication scanner. The CSP
supports multiple line protocols, and provides character buffering and cycle steal
data transfer into main storage. The CSP also does other repetitive operations
such as ASCII/EBCDIC translation for BSC lines.
Front-End Scanner Low-Speed
The FESL provides 'bit service' (serialization/deserialization) and 'line service'
(supports link protocols and line interfaces).
Serial Link
The serial interface link between the FESL and LICs provides an easier adaptation
to configuration changes. The twisted-pair interface eliminates the fixed positional
relationship between scanner and LIC. The flexible nature of the serial link allows
the CSP and the connecting LICs to be in any of their positions within the 3745.
Depending on the model, the 3745 can have scanners and LICs independently
added to support performance or connectivity requirements.
This design provides effective use of scanner resource.
Selective Scanning
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As in the 3745-210/310/410/610, a new logical addressing technique allows
scanning of only the activated lines. When all the lines of a LIC are deactivated, it
is removed from the scanning sequence (except for X.21 lines). This increases the
number of LICs that can be attached to the CSP. It is possible to exceed 100%
line weight when configuring the 3745. The only constraint is that the weight of
activated
lines must not exceed 100%.
4-8
IBM 3745 Models 130, 150, 170: Introduction
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