Search found 451 matches

by Dio
Thu Oct 17, 2013 7:25 am
Forum: Hardware
Topic: Detailed STE DMA audio documentation?
Replies: 12
Views: 5086

Re: Detailed STE DMA audio documentation?

The accurate sample frequencies are 8.010613MHz divided by 160, divided further by 1, 2, 4 or 8.
by Dio
Wed Oct 16, 2013 12:23 pm
Forum: Demos - General
Topic: List of ST/STE demos that can't be imaged (=protected demos)
Replies: 50
Views: 55231

Re: List of ST/STE demos that can't be imaged (=protected de

And I can also get off my backside and make some myself :) .
by Dio
Wed Oct 16, 2013 10:12 am
Forum: Demos - General
Topic: List of ST/STE demos that can't be imaged (=protected demos)
Replies: 50
Views: 55231

Re: List of ST/STE demos that can't be imaged (=protected de

OK, so that's cutting it down to 54 bytes overhead per sector. That's small enough to physically fit as long as the drive runs at or below nominal speed. But the particular structures aren't remotely preserved after you write the sectors - the sector write will spill over and start overwriting the 0...
by Dio
Wed Oct 16, 2013 7:04 am
Forum: Hardware
Topic: Detailed STE DMA audio documentation?
Replies: 12
Views: 5086

Re: Detailed STE DMA audio documentation?

And finally (just out of couriosity): Is video overscan "colliding" with audio? Is audio data transfer really limited to the sync phase or is it exteding into the borders and may thus collide with opened borders? I don't think it's limited to sync time - it's simpler just to fill the FIFO on any MM...
by Dio
Tue Oct 15, 2013 1:25 pm
Forum: Demos - General
Topic: List of ST/STE demos that can't be imaged (=protected demos)
Replies: 50
Views: 55231

Re: List of ST/STE demos that can't be imaged (=protected de

AtariZoll wrote:Here is short part from my floppy format/copy SW:
Thanks for that, very interesting. Can you tell me what each of the GAP sizes is used for?
by Dio
Tue Oct 15, 2013 9:54 am
Forum: Demos - General
Topic: List of ST/STE demos that can't be imaged (=protected demos)
Replies: 50
Views: 55231

Re: List of ST/STE demos that can't be imaged (=protected de

Dio, I really don't get why you write this. Many people used Hyperformat with success, and even some commercial games have such, 11 sect/track format. I wrote it because I've looked at the spec. The timing for write sector (after the index has been recognised) is fixed and very tight: 23-byte delay...
by Dio
Mon Oct 14, 2013 5:47 pm
Forum: Demos - General
Topic: List of ST/STE demos that can't be imaged (=protected demos)
Replies: 50
Views: 55231

Re: List of ST/STE demos that can't be imaged (=protected de

you can make 880K in regular format. More than it is possible, but only little - and using read track. Based on the numbers in the FDC manual, I can't see a way to legally build an 11-sector regular format disk that can be written to by the FDC. The ST nominally gets 6250 bytes per disk but there's...
by Dio
Fri Oct 04, 2013 9:43 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

Thanks for the explanation. Does this mean the MMU consults a memory map to know whether it needs to do this for a specific memory address or not? My expectation is that MMU owns DTACK for everything going through the gateway and the timing of it is run by the same state machine that manages RDAT, ...
by Dio
Thu Oct 03, 2013 10:24 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

I'll take your word for it :) It's beyond my knowledge - to me it's "the same bus". There's two data buses in the ST, the CPU bus and the DRAM / Shifter bus. The two are bridged by a bus gateway - a buffer and a latch, controlled by RDAT, WDAT and LATCH on the MMU. The DRAM bus is segmented by MMU ...
by Dio
Thu Oct 03, 2013 1:21 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

Once I realised that both changes to FREQ (synchro) and RES (videomode) only need to be detected in GLUE the rest of my wakestate-hypothesis fell nicely into place. This also means, to get back to your comment, that as far as I understand there's no video domain for either of these switches in the ...
by Dio
Wed Oct 02, 2013 10:12 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

Remember, so far everything points to STE behaving as ST wakestate 1 - that is - 0 cycle offset between CPU and GLUE. This is fully logical due to MMU and GLUE having been merged into one in the STE. So, when comparing the above to Paolo's Excel-sheet all ff8260 timings in there should be subtracte...
by Dio
Fri Sep 27, 2013 10:21 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

I think that's exactly what happens. It looks to me like the MMU queries the status of DE at the start of each CPU phase to determine what the next video phase will be, and we know there's no fixed alignment between the two. That would imply a latency of 2-5 cycles, but we see 3-6; so either it quer...
by Dio
Fri Sep 27, 2013 10:08 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

I think you're being too complicated over DE. I'd be really surprised if it's not (DE = H and V). It's a big plus to think like a hardware engineer. What's cheapest? What's easily made out of TTL circuits? (The custom chips were all prototyped in wirewrap). NMOS allows really quite cheap comparisons...
by Dio
Fri Sep 27, 2013 7:18 am
Forum: FPGA Chat
Topic: Exact ST video timings?
Replies: 20
Views: 14605

Re: Exact ST video timings?

Where did you get that numbers from? Do both fields really have the same number of lines? Since 32Mhz/2/1024/312.5 is _exactly_ 50Hz i'd assume that it's alternating 313/312 lines. Which in turn would mean that my current scanline emulation which just dims the second of a scan doubled line could be...
by Dio
Sat Sep 21, 2013 10:23 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

I wonder if at least BLANK is not set/cleared but inverted by the state machine. Maybe that's even true for other signals. I reckon this is unlikely. I can't see any sign of it in the traces - plus an S/R flip-flop is two gates while a toggling flip-flop is six. I agree that it's likely that the st...
by Dio
Thu Sep 19, 2013 7:03 am
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

There isn't a convention on these things. Indeed, I'm aware of more computers whose counter origin is the top-left screen fetch than it being tied to the sync positions. The 14-byte line case may demonstrate there isn't one falling edge of HSYNC though. Plus that then creates the problem with needin...
by Dio
Wed Sep 18, 2013 9:02 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

So firstly, the DE to shifter LOAD is variable depending on the wakeup state. Hence my notation DL3-DL6 for each wakeup state. Then if you look at the traces, you can see where the writes to the registers are happening. Look at the A23 line - those indicate accesses to memory addresses with the top ...
by Dio
Wed Sep 18, 2013 7:40 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

There's a subtlety here: there is no "Emulator cycle 56". It is "MMU/CPU cycle 56" and DE is not synchronised to it. The MMU operates a 4 (8MHz) clock state machine. For two of those cycles it gives the DRAM bus to the CPU and for the other two it gives them to video or refresh. Let's call these cyc...
by Dio
Tue Sep 17, 2013 7:18 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

Yes, that's what I measured on that case.
by Dio
Tue Sep 17, 2013 5:28 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

If you really want to get that detailed I can give you a zip of all the traces, which you can load into the software even without the OLS board...?
by Dio
Tue Sep 17, 2013 12:26 pm
Forum: Hardware
Topic: ST vs Amiga : advantages/disadvantages
Replies: 180
Views: 41859

Re: ST vs Amiga : advantages/disadvantages

On a non-display scanline it's 128. (512 / 4 == 128 video or refresh phases). On a display scanline it's 48 (80 of the phases are used to read the 160 byte line).
by Dio
Tue Sep 17, 2013 11:28 am
Forum: Hardware
Topic: ST vs Amiga : advantages/disadvantages
Replies: 180
Views: 41859

Re: ST vs Amiga : advantages/disadvantages

Here's a trace showing the refresh counter - this is capturing the various signals at the DRAM: http://www.v11.co.uk/st/logic/dram_refresh_counter_before_screen_2b_2a.png The first two columns of numbers are the refresh counter in the MMU - note RAS but no CAS. This is just as the display starts, so...
by Dio
Tue Sep 17, 2013 11:20 am
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

OK, blizzard of diagrams. Note that these are mostly captured at a quite heavily quantised sampling rate - for example, in the DE to screen latency capture it's 20MS/S so there's 50ns quantisation, hence why the 8MHz clock looks ropy as hell and signals which should be nominally pretty simultaneous ...
by Dio
Tue Sep 17, 2013 6:21 am
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

Good point - the DE to load latency must shift the timing slightly (after all, it's visible on the monitor).

I have plenty of webspace. I just need to get organised :) .
by Dio
Mon Sep 16, 2013 10:22 pm
Forum: Coding
Topic: horizontal scrolling on ST
Replies: 576
Views: 184402

Re: horizontal scrolling on ST

Of course, but, poking the Shifter (820a) at cycle 52 will produce an NTSC starting position instead of PAL - and if the actual pixels also are displayed at cycle 52 (and 56 respectively) then I can't imagine how there would be time for anything else to be involved. They're not. They appear on the ...

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