Tnc Data Interfaces; Rs-232-C/V.24 Interface - HEIDENHAIN TNC 415 Technical Manual

2 TNC data interfaces

2.1 General
Besides the standard RS-232-C/V.24 interface, the TNC 407/415 has another data interface, the
RS-422/V.11, which is used for long transmission distances.
The two interfaces differ only in the construction of their hardware (signal lines, signal levels and pin
layout).The data format and transmission protocol are the same for both interfaces.
The HEIDENHAIN FE 401 floppy disk unit, ME 101 magnetic tape unit (no longer in production) and
external devices with appropriate data interfaces (computers, printers, readers, punches) can be
connected via either RS-232-C/V.24 or RS-422/V.11 interfaces.
The two interfaces of the TNC can also be operated in parallel; for example, a program can be read
in via the RS-232-C/V.24 interface and simultaneously executed, while a data file could be read in via
the RS-422/V.11 interface.
However, an external interface for level conversion must be used when connecting a floppy disk unit
and magnetic tape unit to the RS-422/V.11 interface.
Two transmission protocols are available for data transfer:
– Standard data transmission protocol
– Data transfer with Block Check Character (BCC)
The data format and control characters concerned are freely configurable within the framework of
these protocols.

2.2 RS-232-C/V.24 interface

RS-232-C is the designation of a serial interface based on the EIA standard of the same name and
can be used for transmission rates up to 19,200 bits/sec. Data transfer is executed asynchronously,
with a start bit before each character and one or two stop bits after each character. The interface is
designed for transmission distances of up to 30 metres.
The RS-232-C interface has been adopted with slight modifications and has been introduced into
Europe as the V.24 interface. The relevant German standard is DIN 66020.
2.2.1 Hardware
The physical connection between two RS-232-C/V.24 interfaces is an asymmetrical line, i.e. the
common ground connection between transmitter and receiver is used as a return wire.
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