HEIDENHAIN TNC 407 (243 020) Technical Manual - Manual (Page 650)

01.98
TNC 407/TNC 415/TNC 425 1 Introduction 8-3
1 Introduction
When operating a computer system (PC, Controller), a wide variety of peripherals, such as printers,
external memories (floppy-disk drives; hard disks) or other computer systems, can be installed in
addition the Central Processing Unit (CPU).
Communication between the CPU and the peripherals is made possible by using a data interface.
Communication requires facilities for transferring data to the peripherals and of course, physical
connection via a transmission line. Peripheral device control and communication, via the interface, is
generally the responsibility of the computer system. The computer system therefore has to meet
certain requirements.
The interfaces, which primarily consist of the physical links between the computer system and the
peripherals, need appropriate software in order to control the transfer of information between the
individual units. The relationship between hardware and software, which fully defines an interface, is
illustrated by the following diagram:
Computer Software Hardware Software Peripheral
e.g. PC,
Controller e.g. Printer,
external memory
Interface
The "hardware" in the diagram covers all the physical components, such as circuit construction, pin
layout, electrical characteristics, etc. The "software" includes, for example, the drivers for the output
modules, which are part of the operating software both of the computer system and the peripherals.
Due to the wide variety of computers, controllers and peripherals, standard interfaces have been
introduced, which, in an ideal situation, enable extremely varied devices to be connected to each
other.
Such standards include, for example, the RS-232-C/V.24 and RS-422/V.11 interfaces, which are
described in detail later.