RAM or registers for having 16*8 bit memory

• Oct 25, 2005

• #1

omid219

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Hi

I need a 16*8 bit memory in my design. I'm not sure wether it is better to use RAM or implement it with registers. I know that for big memories it is better to use ram because of the area and power. But at the same time, it is advised to not use ram for small values because of the test (mbist) overhead. So, what is decision value? Is ther any role of thumb to say when we should go for ram or registers(file)?

Thanks

 

• Oct 25, 2005

• #2

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alexz

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Re: ram or registers?

Look at FRAM
I have not worked with it myself, but people like it

 

• Oct 25, 2005

• #3

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eeeraghu

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Re: ram or registers?

Depends on the size, Registers use max of the area and even the synthsizing and other issues are there(lots of time), For a RAM there are memory compilers where we can use the availaibility. and using ram is almost like an error free design.

By take care

 

• Oct 25, 2005

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Matrix_YL

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ram or registers?

I think that it maybe depend on your device ,different device have different Block RAM and Distribute RAM so you can chose which one is best for you design !

 

• Oct 26, 2005

• #5

omid219

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Re: ram or registers?

Distributed or Block RAM are for the FPGA, but our target is IC.

 

• Oct 26, 2005

• #6

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Yun Lin

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ram or registers?

Compare them and choose the best.

 

• Oct 26, 2005

• #7

omid219

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Re: ram or registers?

Compare them and choose the best.!!!!!!

Some times it is better to keep quiet.......

 

• Oct 26, 2005

• #8

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eda_wiz

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ram or registers?

16x8 bit is very small .. just 128 Flipflops. I will surely go for simple verilog Registers.

We use Foundry supplied register files for 512bit -5Kbit .. and SRAM for more than 5 Kbits. may be varying depending on fab and process.

If you have the foundry supplied memory compilers for RAM and REGISTER FILE you can generate memory and see the footprint given by it .

 

• Oct 27, 2005

• #9

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kelvin_bao

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ram or registers?

I agree with whizkid.128bit is not very big.

if your ram is bigger than ks,then you will choose the true ram from foundry.

 

• Dec 23, 2005

• #10

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greensand

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ram or registers?

It depends on the area you have.
If you have enough area, DFF is the choice.
Because it's simple and safe.

 

• Dec 23, 2005

• #11

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Nandy

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Re: ram or registers?

In our design flow, picking RAM or FF is decided by a perl script to calculate area. I don't know the detail of the script. The basic idea is one FF is about 6 times larger than one latch, two row of FFs wrapping around RAM input/output, pluse Mbist overhead.
If blindly selecting, deep fifo should use RAM. Less than 16 depth fifo would have less area by using FFs.

Nandy
www.nandigits.com
Netlist Debug/ECO in GUI mode.

 

• Dec 23, 2005

• #12

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palosian

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ram or registers?

Compare them and choose the best.!!!!!!

Some times it is better to keep quiet.......

 

• Dec 24, 2005

• #13

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jackson_peng

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ram or registers?

it is highly wasteful on area, when the RAM size is small, usually less than 512W, because, the high data bus width, will cause the memory block very large.

maybe, you could turn to register file, if you do concern the power consumption

 

• Dec 24, 2005

• #14

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andromeda

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Re: ram or registers?

usually companies have latch or register arrays for small memory sizes (lets say up to 32x32)
those has for example 2+ times smaller area then flops (share some stuff, latches are smaller then flops)
has 1 read and 1 write port usually, or several version with different number of ports
you still need to do BIST on those memories

 

• Dec 25, 2005

• #15

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Re: ram or registers?

I tell you should use FF ,because it safe

 

• Dec 25, 2005

• #16

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ram or registers?

compare both of them..and choose the suitable and best..and yes..no compromise in quality also..

 

• Dec 25, 2005

• #17

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anjali

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Re: ram or registers?

i too prefer FFs because 16X8 is a small memory.

 

• Dec 26, 2005

• #18

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elecs_gene

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Re: ram or registers?

hi
i just wanted to know one thing.it is prefarrable we go for registers,to improve timing.for improving area as well power,we prefer RAM..am i right??so,based on requirement u choose which suites ur require ment.

regards

 

• Dec 27, 2005

• #19

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silencer3

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ram or registers?

a genral rule for useing REG or RAM is,

If memory requirement is Less deep with High width, then use REG implementation.

If memory requirement is too deep (size is more) with stanbdard data width, then better to use RAM.

 

• Dec 27, 2005

• #20

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Sceadwian

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ram or registers?

If what other people use is any indication of what's best, Atmels processor line has a 32*8 general purpose register file on all of it's AVR micro controllers.