iCE40: I/O toggle rate, hard numbers needed

[Aleksandar Kuktin]

Hi all.

Can someone please make my life easier by solving a dilemma? How many
signal transitions per second can iCE40's I/O handle? HX devices.

The datasheet has a table called "Maximum sysIO Buffer Performance" which
lists numbers in MHz. Are these numbers full-cycle (two transitions) or
half-cycle (one transition)?

There is also a table called "iCE40 External Switching Characteristics -
HX Devices" which has some numbers on what appear to be signal setup and
hold times, plus skew. Working these numbers out, one gets an estimate
that does not conform to the other table (it is lower).

So what is it? How many times can I toggle or be toggled?

FWIW, I'm trying to figure out how big a screen I can drive with it. I'm
hoping for B101AW03-V1 which is a 1024x800 @60Hz, uses a three+one FSD-
Link but needs to be driven at ~383.6 Mts (million signal transitions per
second). I also want to figure out if I can interface to a DDR2 memory
interface at 166 MHz, or if I'm stuck with 125 MHz.

 

[rickman]

On 9/10/2016 8:06 AM, Aleksandar Kuktin wrote:

Hi all.

Can someone please make my life easier by solving a dilemma? How many
signal transitions per second can iCE40's I/O handle? HX devices.

The datasheet has a table called "Maximum sysIO Buffer Performance" which
lists numbers in MHz. Are these numbers full-cycle (two transitions) or
half-cycle (one transition)?

There is also a table called "iCE40 External Switching Characteristics -
HX Devices" which has some numbers on what appear to be signal setup and
hold times, plus skew. Working these numbers out, one gets an estimate
that does not conform to the other table (it is lower).

So what is it? How many times can I toggle or be toggled?

FWIW, I'm trying to figure out how big a screen I can drive with it. I'm
hoping for B101AW03-V1 which is a 1024x800 @60Hz, uses a three+one FSD-
Link but needs to be driven at ~383.6 Mts (million signal transitions per
second). I also want to figure out if I can interface to a DDR2 memory
interface at 166 MHz, or if I'm stuck with 125 MHz.

I see what you mean. I'm not familiar with the video you are
describing, but DDR2 uses a clock at the same max toggle rate as the
data. This is usually done with a pair of FFs in the IOB which can
multiplex the double rate data into a pair of single rate data streams
using the same clock rate in either direction. But then you likely know
all that.

I found an older version of an app note about LVDS I/O in the iCE40
parts. Bottom of page 1 shows a table with input and output frequencies
of 525 and 480 MHz respectively. Is that fast enough? Although they
don't say the iCE40 will work at those speeds, lol. The newer rev of
the document doesn't include this table and makes no mention of the data
rates possible.

http://www.prevailing-technology.com/publications/TN1253.pdf

--

Rick C