Previous Thread
Next Thread
Print Thread
Page 37 of 55 1 2 35 36 37 38 39 54 55
rfka01 #107329 09/17/16 09:43 AM
Joined: Apr 2012
Posts: 190
B
Senior Member
Offline
Senior Member
B
Joined: Apr 2012
Posts: 190
@Crazyc: i am curious. How did you figure out the various bit masks (for "offset") in VRAM_W? Via schematics?

I am thinking of statements like
Code:
WRITE16_MEMBER(vt240_state::vram_w)
{
...
	offset = ((offset & 0x30000) >> 1) | (offset & 0x7fff);

Last edited by Bavarese; 09/17/16 01:30 PM.
rfka01 #107332 09/17/16 02:18 PM
Joined: Jan 2012
Posts: 869
Likes: 6
C
Senior Member
Offline
Senior Member
C
Joined: Jan 2012
Posts: 869
Likes: 6
In https://archive.org/stream/bitsavers_dec...ge/n20/mode/1up address line 14 is ignored while 15 and 16 are routed to other circuitry.

rfka01 #107351 09/19/16 05:27 PM
Joined: Apr 2012
Posts: 190
B
Senior Member
Offline
Senior Member
B
Joined: Apr 2012
Posts: 190
Palette and Vsync statements are in place now.

I had modest successes with freeware games PACMAN, DOODLE and SCRAM (the last one displays a monochrome intro pic with too much space in between).

Text seems totally broken (right to left). Guess "hgdc_draw_text" must be implemented, first eek



Could someone have a look at the offsets in "vram_w" and "hgdc_display_pixels", please?

https://dl.dropboxusercontent.com/u/37819653/BANNISTER/2016_09_19_RAINBOW_CPP.txt

Without schematics or intimate knowledge of the 7220, it seems too much trial & error (i do not even own the hardware).

Perhaps there a circuit diagram of the Rainbow-100 graphics option (part number should be 54-15688 or PC1XX-BA)...?

Last edited by Bavarese; 09/19/16 06:35 PM.
rfka01 #107358 09/20/16 09:29 AM
Joined: Apr 2012
Posts: 190
B
Senior Member
Offline
Senior Member
B
Joined: Apr 2012
Posts: 190
We actually have schematics here.

I'd appreciate hints, though (see previous post) smile

There is also a 'new' piece of DEC hardware i encountered during my search, the so-called Mini-Exchange. It was a serial 8 port serial X switch with DOS support (Xattach, XDetach). Sort of an early Laplink.

Thanks to all uploaders (wink Rfka).

Last edited by Bavarese; 09/20/16 09:31 AM.
rfka01 #107391 09/23/16 12:39 PM
Joined: Apr 2012
Posts: 190
B
Senior Member
Offline
Senior Member
B
Joined: Apr 2012
Posts: 190
Wow, 2 of 13 tests from Graphics Diagnostic Disk pass (presence detect, FIFO). smirk

Ok, the PAL array already dumped does some modifications on bits before they are written back to the bit map memory (guess: ALU / plane select).

Now i am unsure about the 7220 clock. Is it really (E31) 31.188 Mhz / 4 = 7.797 Mhz ...?

A 31.188 quarz does not seem to exist in XTAL.H...

Datasheets says "7220 is available in 4.0 , 5.0, and 5.5 Mhz versions, 7220A in 6.0, 7.0, and 8.0 Mhz"




Pic: there is a plethora of good tests for different 7220 modes (complete with explanations and loop option...just press ALT for Help or L to loop after a failure)

Last edited by Bavarese; 09/23/16 01:27 PM.
rfka01 #107392 09/23/16 01:19 PM
Joined: Mar 2001
Posts: 16,751
Likes: 29
R
Very Senior Member
Offline
Very Senior Member
R
Joined: Mar 2001
Posts: 16,751
Likes: 29
That diagnostic could be useful for sorting out some of the dark corners of the 7220 emulation.

Joined: May 2009
Posts: 1,946
Likes: 13
J
Very Senior Member
Offline
Very Senior Member
J
Joined: May 2009
Posts: 1,946
Likes: 13
Originally Posted By R. Belmont
That diagnostic could be useful for sorting out some of the dark corners of the 7220 emulation.


True, but that "erratic interrupt" failure is slightly alarming. Depending on how demanding the tests themselves are, it could be a real pain to get them all passing, which is something that I'm encountering currently with the Fairlight CMI driver.

rfka01 #107444 09/27/16 07:41 PM
Joined: Apr 2012
Posts: 190
B
Senior Member
Offline
Senior Member
B
Joined: Apr 2012
Posts: 190
The NEC 7220 is rather complex, and several features are missing in the current code (RMW cycles for example).

I now have a playable version of SCRAM... only the diagnostic disk is unimpressed. There is certainly a long way to go.

BTW, i found a good article by Guido Dampf (from 1986, in German) about the inner workings of this chip, with Turbo Pascal source. An abridged version in English is somewhere, too.

Crazyc, do you happen to know it?

I plan to submit my current status soon and hope for improvements by others. As stated above, Pacman, Doodle and Scram offer fine test cases (apart from the GDC diagnostic disk).


Last edited by Bavarese; 09/27/16 07:55 PM.
rfka01 #107446 09/27/16 07:54 PM
Joined: Jan 2011
Posts: 216
Likes: 1
Senior Member
Offline
Senior Member
Joined: Jan 2011
Posts: 216
Likes: 1
This makes me want to poke a the quad qbus 7220 board that came in the Calcomp branded Terak that I have again. Problem is I have no software for it.

Bavarese #107447 09/27/16 07:59 PM
Joined: Jan 2012
Posts: 869
Likes: 6
C
Senior Member
Offline
Senior Member
C
Joined: Jan 2012
Posts: 869
Likes: 6
Originally Posted By Bavarese
The NEC 7220 is rather complex, and several features are missing in the current code (RMW cycles for example).
We do do rmw cycles for everything except the case where the whole byte/word is written directly, we just to them too fast (which may need to be fixed for the 9801 but nothing else seems to be that timing sensitive).
Originally Posted By Bavarese
Crazyc, do you happen to know it?
German? Nope.

Last edited by crazyc; 09/27/16 08:00 PM.
Page 37 of 55 1 2 35 36 37 38 39 54 55

Link Copied to Clipboard
Who's Online Now
2 members (Lord Nightmare, belegdol), 26 guests, and 3 robots.
Key: Admin, Global Mod, Mod
ShoutChat
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Forum Statistics
Forums9
Topics8,940
Posts117,525
Members4,994
Most Online890
Jan 17th, 2020
Forum Host
These forums are hosted by www.retrogamesformac.com
Forum hosted by www.retrogamesformac.com