Onchip SRAM Vs Registers

[john.deepu]

Hi all,
Can anyone tell me what is the threshold point(memory size) to opt
for Onchip SRAM instead of FlipFlops , considering the Power&Area. In a
module I have ~5Kbit of memory implemented as verilog registers. I
would like to know the Power/Area savings if I switch to SRAM instead
of Flipflops. I use .13u process.
Any links/documents in this regard are highly welcome.
Thanks
Deepu John

 

[Peter Alfke]

John, your question seems to relate to ASIC design. This newsgroup
deals with FPGAs where you select and then use a given architecture.
That means the trade-offs are different.
Modern FPGAs have SRAM blocks of various sizes, from 512 bits to 18 k
bits and even larger. Xilinx offers the RAM option in the Look-up
Tables (LUTs), which can even be used as shift registers.
The designer's decision is to use available resources, not to design
latches or flip-flops.
This can lead to peculiar design optimizations when a certain resource
is abundant and not all used, e.g. BlockRAMs.
5k bit fits very comfortably in one 18 kbit dual-ported BlockRAM, but
would take an inordinate amount of LUTs, even at 16 bits per LUT. You
decide.
Peter Alfke, Xilinx