Browse Prior Art Database

CMOS Programmable I/O Circuits

IP.com Disclosure Number: IPCOM000115068D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 71K

Publishing Venue

IBM

Related People

Cao, TA: AUTHOR [+4]

Abstract

In any system, driver and receiver play an important role since they have to communicate back and forth between chip to chip. Without properly set of driver/receiver the system will not meet top performance and sometime does not work. A set of driver/receiver has been designed such that driver can be used as a termination device which is called far end pull up or pull down termination operating at 200MHZ or higher.

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CMOS Programmable I/O Circuits

      In any system, driver and receiver play an important role since
they have to communicate back and forth between chip to chip.
Without properly set of driver/receiver the system will not meet top
performance and sometime does not work.  A set of driver/receiver has
been designed such that driver can be used as a termination device
which is called far end pull up or pull down termination operating at
200MHZ or higher.

      This disclosure proposes a method that can be used to terminate
a net properly without using any additional device like resistor.

      As a test requirement, driver and receiver have to be in the
common IO (CIO) book which means driver and receiver have to be in a
pair.  In ordr to work with this restriction and also take the
advantage of driver already in the macro, the driver has been
implemented such that output stage can be used as a termination
device.

      For this disclosure the application is Uni direction.  As shown
in Fig. 1, the driver on the source sends signals to receivers which
are at drop 1, 2, and 3 on the other end.  The termination needs to
be at drop.  The driver has been designed so that all of the enable
signals have to be met the test requirement as shown in the table
below:

      Fig. 2 shows the output stage of the driver at drop 3.  It is a
termination depending on how you use it.  In this case, pull up and
pull down are two solutions:
  1.  Pull up case: Din...