On 8/10/2022 1:19 PM, Anthony Ortiz wrote:
>> You mentioned DMA so I'm thinking that's the timing you are going for.
>> The IIgs hardware reference says (in reference to cards that work on
>> other Apple II models) that they will *probably* work if they assert and
>> remove the /DMA signal within 200 nanoseconds of the rising edge of
>> phase 0. It also says that normally the IIgs should be running at 1.024
>> MHz when performing DMAs. There are exceptions to this if you are only
>> accessing fast ram or rom.
>> Also with the IIgs you need to set the DMA bank register.
>>
>> If you are using a logic device (FPGA, etc.), here is a link to Alex
>> Freed's verilog code for DMA timing on an Apple IIe which may help:
>>
>>
https://sourceforge.net/p/jatcb/code/HEAD/tree/dma.v
>>
>> Lastly, I like to synchronize all the clocks on the card whether or not
>> I'm using the 7Mz Apple clock as the system clock or a clock on the card.
>>
>> Charlie
>
> Hey Charlie,
>
> I'm new to VHDL so I was trying to trigger on both the rising/falling edges of 7M to create a counter that offsets from Phase0 rise/fall, that way I could use the counter as a point where to perform certain logic such as read and writes.
I program in verilog and I was completely new to it when I started with
the Carte Blanche card.
I'm still pretty much a novice.
However, I quickly learned that I know nothing and that just because
it's valid VHDL doesn't mean it's synthesizable, lol. I'm just going to
create a 100mhz clock so that I have 10ns granularity and use that instead.
I found that out too. ;-)
It is my understanding that triggering on both the rising and falling
edge of a clock signal won't work because the flip-flops in the chip
don't support double clocking. At least they don't on the FPGAs on the
Carte Blanche and Carte Blanche II card.
>
> You mention the Carte Blanche; have you done a lot of prototyping with it?
Most of what I've done is with video. I originally modified Alex
Freed's JAT code for the Carte Blanche so that I could have the colored
text, background and borders on a //e (like a IIgs has).
My next project was to make a video only card for the IIgs with the SHR
video modes.
After that I made a video card for the //e that displays SHR graphics.
I also added code to allow loading a bitstream to the flash memory on
the Carte Blanche from the Apple //e.
When the Carte Blanche II came out I moved my projects to it.
Also added HDMI output and 800x600 resolution so that the IIgs side
borders are visible.
> Do you have any projects you're working on?
One project that I started quite a while ago is using the onboard micro
SD card as a hard drive (something like the CFFA3000 does with USB)
while still maintaining the VGA/HDMI video.
Unfortunately, life gets in the way and I haven't done much with it lately.
Here's my website for more information:
http://noboot.com/charlie/Charlie's%20Stuff.htm
Charlie