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IP.com Disclosure Number: IPCOM000110598D
Original Publication Date: 1992-Dec-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Deremer, RL: AUTHOR [+4]

Abstract

A method of powering an EIA-232 to TTL electrical level converter from the EIA-232 interface is disclosed. This method allows attachment from a PC ASYNC adapter card to the AS/400* machine interface without requiring an external power supply and also allows reduced package size.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 99% of the total text.

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       A method of powering an EIA-232 to TTL electrical level
converter from the EIA-232 interface is disclosed.  This method
allows attachment from a PC ASYNC adapter card to the AS/400* machine
interface without requiring an external power supply and also allows
reduced package size.

      This design, as shown in the figure, uses the EIA 232 signals
on the PC ASYNC adapter to power the signal level converter module.
This allows elimination of an external transformer.  The circuit,
including the signal level converter, can be packaged in the cable
connector housing.

      Typical EIA 232 to TTL signal converter modules require 3
voltages for operation: VCC (+5 V), VDD (between +5 V and +15 V), and
VCC (between -5 V and -15 V).

      DTR is constantly active when this interface is being used and,
therefore, is used by this design to provide both VCC and VDD.  An
adjustable precision shunt regulator is used to hold VCC at a nominal
+5 V.

      The data exchange protocol used on this interface is half
duplex (data in one direction at a time); therefore, Transmit Data is
held at an inactive or low voltage state when there is no data to
transfer from the PC to the AS/400 and can be used to provide VSS.
The two signals which have to be driven back to the PC by the AS/400
(CTS and Receive Data) are either at a high voltage state or ignored
when data is being transmitted from the EIA-232 side.
*  Trademark of IBM Corp....