FLEX 10K Embedded Programmable Logic Family Data Sheet
Larger blocks of RAM are created by combining multiple EABs. For
example, two 256 × 8 RAM blocks can be combined to form a
256 × 16 RAM block; two 512 × 4 blocks of RAM can be combined to form
a 512 × 8 RAM block. See Figure 3.
Figure 3. Examples of Combining EABs
256 × 16
512 × 8
256 × 8
512 × 4
256 × 8
512 × 4
If necessary, all EABs in a device can be cascaded to form a single RAM
block. EABs can be cascaded to form RAM blocks of up to 2,048 words
without impacting timing. Altera’s MAX+PLUS II software automatically
combines EABs to meet a designer’s RAM specifications.
EABs provide flexible options for driving and controlling clock signals.
Different clocks can be used for the EAB inputs and outputs. Registers can
be independently inserted on the data input, EAB output, or the address
and WEinputs. The global signals and the EAB local interconnect can drive
the WEsignal. The global signals, dedicated clock pins, and EAB local
interconnect can drive the EAB clock signals. Because the LEs drive the
EAB local interconnect, the LEs can control the WEsignal or the EAB clock
signals.
Each EAB is fed by a row interconnect and can drive out to row and
column interconnects. Each EAB output can drive up to two row channels
and up to two column channels; the unused row channel can be driven by
other LEs. This feature increases the routing resources available for EAB
outputs. See Figure 4.
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