Answers Database

96/98 DATA BOOK: RAM: Write enable pulse width following active edge of WCLK.


Record #3423

Product Family:  Documentation

Product Line:  Other

Problem Title:
96/98 DATA BOOK: RAM: Write enable pulse width following active edge of
WCLK.



Problem Description:
Keywords: Data, book, Single port, Dual port, edge triggered,
RAM, NOTE, Twps, WCLK, write clock, WE, write enable

Urgency: Standard

General Description:
The notes on pages 4-16 and 4-17 of the 9/96 Data Book and
pages 4-13 and 4-15 of the 1/98 Data Book say:

"The pulse following the active edge of WCLK (Twps in Figure
<#>) must be less than one millisecond wide.  For most
applications, this requirement is not overly restrictive;
however, it must not be forgotten.  Stopping WCLK at this point
in the write cycle could result in excessive current and even
damage to the large devices if many CLBs are configured as
edge-triggered RAM."

These notes are misleading.  They apply only the XC4000E
devices.  In the 4000EX, 4000XL, 4000XV, and subsequent
families, this problem has been resolved.


Solution 1:

Ignore this warning if you are using 4000X parts.



End of Record #3423