ICE40 Logic Cells

[rickman]

I was aware that the ICE40 devices have some limitations compared to
other devices that are not so cost and power constrained. Until now the
apparent lack of LUT RAM escaped me. I guess it is one of those
features that is so ingrained in my mind that I never noticed they don't
talk about it. The LP family has a very low end member with only 384
LUTs and *no* block RAM, so I was considering what I might do with the
LUT RAM. Not much. They don't mention the LUT RAM anywhere and barely
mention the LUTs as ROM only peripherally, but I'm pretty sure that is
available since it is the same as logic.

Wow, the 384 LUT part has no RAM at all, so it ends up being incredibly
limited.

--

Rick

 

[Rob Gaddi]

On Fri, 05 Dec 2014 15:16:03 -0500
rickman <gnuarm@gmail.com> wrote:

I was aware that the ICE40 devices have some limitations compared to
other devices that are not so cost and power constrained. Until now the
apparent lack of LUT RAM escaped me. I guess it is one of those
features that is so ingrained in my mind that I never noticed they don't
talk about it. The LP family has a very low end member with only 384
LUTs and *no* block RAM, so I was considering what I might do with the
LUT RAM. Not much. They don't mention the LUT RAM anywhere and barely
mention the LUTs as ROM only peripherally, but I'm pretty sure that is
available since it is the same as logic.

Wow, the 384 LUT part has no RAM at all, so it ends up being incredibly
limited.

--

Rick

At that point it's basically just a CPLD killer.

--
Rob Gaddi, Highland Technology -- www.highlandtechnology.com
Email address domain is currently out of order. See above to fix.

 

[rickman]

On 12/5/2014 3:54 PM, Rob Gaddi wrote:

On Fri, 05 Dec 2014 15:16:03 -0500
rickman <gnuarm@gmail.com> wrote:

I was aware that the ICE40 devices have some limitations compared to
other devices that are not so cost and power constrained. Until now the
apparent lack of LUT RAM escaped me. I guess it is one of those
features that is so ingrained in my mind that I never noticed they don't
talk about it. The LP family has a very low end member with only 384
LUTs and *no* block RAM, so I was considering what I might do with the
LUT RAM. Not much. They don't mention the LUT RAM anywhere and barely
mention the LUTs as ROM only peripherally, but I'm pretty sure that is
available since it is the same as logic.

Wow, the 384 LUT part has no RAM at all, so it ends up being incredibly
limited.

--

Rick

At that point it's basically just a CPLD killer.

Yes, you are exactly right. Lowest possible price.

They have an ICE40LM line that only uses configuration RAM with no
internal configuration storage. Funny how you can read the data sheet
looking for the raison d'etre of a part but can't see it because of the
marketing crap. I've seen this sub family for a while now and always
thought it was about the hard cores (I2C, SPI, etc). It is about the
lowest possible cost meaning no config storage. I guess the assumption
is the configuration is stored elsewhere for pennies.

--

Rick