XC3S100E Datasheet, PDF (41/193 Pages) Xilinx, Inc – DC and Switching Characteristics

Functional Description
R
Data_in
Internal
DI _Memory
DO
Prior stored data
CLK
WE
DI
ADDR
XXXX
aa
1111
bb
2222
cc
XXXX
dd
DO
0000
MEM(aa)
old MEM(bb)
old MEM(cc)
MEM(dd)
EN
DISABLED
READ
WRITE
MEM(bb)=1111
WRITE
MEM(cc)=2222
READ
DS312-2_06_020905
Figure 31: Waveforms of Block RAM Data Operations with READ_FIRST Selected
Data_in
Internal
DI _Memory
DO
No change during write
CLK
WE
DI
XXXX
1111
2222
XXXX
ADDR
aa
bb
cc
dd
DO
0000
MEM(aa)
MEM(dd)
EN
DISABLED
READ
WRITE
MEM(bb)=1111
WRITE
MEM(cc)=2222
READ
DS312-2_07_020905
Figure 32: Waveforms of Block RAM Data Operations with NO_CHANGE Selected
Setting the WRITE_MODE attribute to a value of
NO_CHANGE, puts the DO outputs in a latched state when
asserting WE. Under this condition, the DO outputs retain
the data driven just before WE is asserted. NO_CHANGE
timing is shown in the portion of Figure 32 during which WE
is High.
34
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DS312-2 (v1.1) March 21, 2005
Advance Product Specification