[Coco] 6809 FPGA

[Dave Philipsen]

Ok, and looking at your message a little closer.  Don't worry that the 
compiler does not allocate logic elements for the ROM.  There are 
specific memory blocks internal to the FPGA that are used for that.  The 
DE0 has a total of 504K bits for memory which amounts to 50-60K of 8-bit 
wide memory.  You should have plenty for the Searle project.

You're getting closer anyway!  The blinking cursor on the screen means 
you've got the clock hooked up correctly and the VGA code is basically 
working.  Probably the only thing keeping your board from coming up is 
getting the ROM right and making sure you have so RAM for it.  Also, 
just go ahead and set the CPU speed down to the the lowest speed at 
first.  I think that's 1 MHz.  When the board comes up then you can 
experiment with increasing it.

Cut and paste the "rollover" warnings and send them to us.  That doesn't 
ring a bell.

Dave Philipsen


On 9/10/2015 10:55 PM, Dave Philipsen wrote:
> Oh, and the 3.3v levels are actually TTL.  They're just a low-voltage 
> version of standard 5v TTL.  Some 5v stuff will actually work with 
> 3.3v signals apparently but you probably would get into trouble 
> driving any 3.3v (LVTTL) with 5v signals.
>
> Personally I would recommend the AS6C4008-55PCN 
> <https://www.mouser.com/Search/ProductDetail.aspx?R=AS6C4008-55PCNvirtualkey56240000virtualkey913-AS6C4008-55PCN> 
> SRAM. It's 512K, 3.3v - 5v tolerant, and only costs around $4.50.
>
> Dave Philipsen
>
> On 9/10/2015 10:36 PM, Dave Philipsen wrote:
>>
>>
>> On 9/10/2015 10:12 PM, Bill Nobel wrote:
>>> Hey all,  I (as some of you know) have been trying to get Grant 
>>> Searles project running on a DE0 Nano. I have made some good 
>>> advancements (Many, many thanks greatly to Roger Taylor and Dave 
>>> Philipsen).
>>>
>>> But I need a little help again.  I took Rogers suggestion of 
>>> updating my Quartus ii software to 15.0 and things did dramatically 
>>> change.  I now have a flashing cursor in the top left corner (which 
>>> should be there upon init of the VGA circuit).  I do have what seems 
>>> like a little sync noise on the background (nothing serious).  I 
>>> could post a pic, but I don’t want to clog the list.  This is all I 
>>> get once I program the DE0 with Grants code.
>>>
>>> I think there is a problem with my selection of the external RAM 
>>> chip (and or the pins I chose to drive it, it is all on GPIO-0) I am 
>>> using a Hitachi 628128 128k SRAM (only using 64k).  I am personally 
>>> thinking, looking at the data sheet for the RAM, that it might not 
>>> handle 3.3v CMOS levels good enough.  Am I correct?
>>
>> Yep, that's a 5v SRAM.  And my guess is you need a 3.3v SRAM.  I am 
>> not positive on what the DE0 does for I/O but if it's like the DE1 
>> then it's 3.3v.
>>
>>
>>>
>>> Also, I do think something is wrong in the ROM code, it does 
>>> compile, but I see in the reports, that there is a rollover in the 
>>> intel HEX code and I don’t see any LU’s allocated for it in the 
>>> compile reports.  I get a total of 44 warnings (most are for pin 
>>> assignments I have not assigned yet).
>>
>> Not sure what you mean by rollover.
>>
>>>
>>> I also see a discrepancy on the pin planner versus the assignment 
>>> editor, The pins are duplicated in the assignment editor, one set 
>>> stating my location assignments, the other just stating location.  
>>> Is this normal?
>>
>> You could have some pins duplicated in the assignment editor if one 
>> line assigns the signal to a pin and another line defines something 
>> else about the pin like whether it has a weak pull-up resistor 
>> attached to it for example.
>>
>>> Bill Nobel
>>>
>>>
>>
>> Dave Philipsen
>>
>>
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