Search found 95 matches

by keli
Wed Nov 01, 2017 11:34 am
Forum: HARDWARE DISCUSSIONS
Topic: Project: HDMI/DVI out for STFM
Replies: 519
Views: 60693

Re: Project: HDMI/DVI out for STFM

The biggest obstacle that I'm dealing with right now is instability. In monochrome, the whole system is reasonably stable, but in colour (50Hz in my case) the length of the video frames are not steady - some are shorter, some are longer. I am working off the theory that this is because of noise in ...
by keli
Sat Oct 28, 2017 10:38 am
Forum: HARDWARE DISCUSSIONS
Topic: Project STacy (STaceX, TOS 2.06 & others)
Replies: 76
Views: 14929

Re: Project STacy (STaceX, TOS 2.06 & others)

Do you happen to have a part number/digikey link/etc. for the mega bus connector on that adapter?
by keli
Fri Oct 27, 2017 3:19 pm
Forum: HARDWARE DISCUSSIONS
Topic: MMU clone project
Replies: 3
Views: 1021

Re: MMU clone project

I do believe however, that this also includes the GLUE logic as it mentions is like ROM & ACIA etc. so likely a lot of this code isn't even needed.. Though if those addresses are removed, it does not look like the MMU does much of anything at all.. It looks almost deceptively simple. In addition to...
by keli
Fri Oct 27, 2017 1:34 pm
Forum: HARDWARE DISCUSSIONS
Topic: Reverse engineer gate logic of the YM2149
Replies: 6
Views: 1231

Re: Reverse engineer gate logic of the YM2149

The & operator in VHDL is the concatenation operator. So chan_amp becomes bits 3,2,1, and 0 from chan_vol plus one additional 1 bit appended to the end. (5 bits in total, with the last bit set to 1) This means 0 becomes 1, 1 becomes 3, 2 becomes 5, 3 becomes 7, etc. Edit: Some more detail. If you lo...
by keli
Tue Oct 24, 2017 7:24 pm
Forum: HARDWARE DISCUSSIONS
Topic: ST SHIFTER operation ?
Replies: 94
Views: 14712

Re: ST SHIFTER operation ?

... or you could use the extra bits to support 65536 colors similar to how the infamous dual shifter mod mentioned in another thread supports 32768 ;)
by keli
Tue Oct 24, 2017 5:05 pm
Forum: HARDWARE DISCUSSIONS
Topic: ST SHIFTER operation ?
Replies: 94
Views: 14712

Re: ST SHIFTER operation ?

I see you're using and storing all 16 bits from the data bus, but on the ST, only 9 bits are stored (12 if you want to support 4096 colors like on the STE.) Since you're building this on a programmable device (and not discreet components), couldn't you save some space by only using 12 bit wide RAM b...
by keli
Sat Oct 21, 2017 3:32 pm
Forum: HARDWARE DISCUSSIONS
Topic: Reverse engineer gate logic of the YM2149
Replies: 6
Views: 1231

Re: Reverse engineer gate logic of the YM2149

I case someone is interested, I found this VHDL implementation of the ym2149: http://www.cpcwiki.eu/index.php/Ym2149
by keli
Sat Oct 21, 2017 12:20 am
Forum: HARDWARE DISCUSSIONS
Topic: Reverse engineer gate logic of the YM2149
Replies: 6
Views: 1231

Re: Reverse engineer gate logic of the YM2149

One question I'm asking myself, how is it that when a channel is disabled in the mixer that setting that channel's volume effectively produces a "pop" sound in the output. It's that characteristic which makes digisound possible. But why does the chip do that? I always imagined it's because when a c...
by keli
Sat Oct 21, 2017 12:02 am
Forum: HARDWARE DISCUSSIONS
Topic: ST SHIFTER operation ?
Replies: 94
Views: 14712

Re: ST SHIFTER operation ?

Have you considered some of the popular FPGA Dev boards such as the KNJN Pluto boards?

They have a small foot print and both Altera and Xilinx options.

I haven't tried them myself, but I was interested in the one with the HDMI port, although that one does not have 5v tolerant I/O
by keli
Tue Oct 17, 2017 11:02 am
Forum: HARDWARE DISCUSSIONS
Topic: ST SHIFTER operation ?
Replies: 94
Views: 14712

Re: ST SHIFTER operation ?

I found this diagram that shows the high level relation ship between DE, HSYNC and BLANK on Jean Louis-Guérin's Atari site

Image

I'm not sure how much more information it adds nor how accurate it is, but I thought I'd post it here just in case.

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