Browse Prior Art Database

Method for Disabling Scan Buffers during Functional Mode

IP.com Disclosure Number: IPCOM000113969D
Original Publication Date: 1994-Oct-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Levitan, DS: AUTHOR

Abstract

On the PowerPC 620* microprocessor, it was determined that if we allow the scan buffers to run during functional mode, they will dissipate one-half (1/2) watt of power. The straightforward way to fix this problem is to route a wire to all of the scan buffers that provided the information whether the chip is in scan mode or in functional mode.

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Method for Disabling Scan Buffers during Functional Mode

      On the PowerPC 620* microprocessor, it was determined that if
we allow the scan buffers to run during functional mode, they will
dissipate one-half (1/2) watt of power.  The straightforward way to
fix this problem is to route a wire to all of the scan buffers that
provided the information whether the chip is in scan mode or in
functional mode.

      The invention is to use the 11 test clock (referred to as the A
clock on the PowerPC 620 microprocessor).  By using it the scan
buffer is only enabled when data is being scanned from the slave part
of the latch to the master part of the latch.  At first this may
appear to be an lssd violation, but it is no more an lssd violation
than the precharged logic where the clock is used to initiate the
precharge logic and the same clock is used to latch the data as shown
in the Figure.

*  Trademark of IBM Corp.