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Joined: May 2004
Posts: 1,007 Likes: 118
Very Senior Member
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Very Senior Member
Joined: May 2004
Posts: 1,007 Likes: 118 |
I don't have a C compiler/SDK either...  Any suggestions?
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Joined: Jul 2009
Posts: 78
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OP
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Joined: Jul 2009
Posts: 78 |
Added the MC6847 fixes (shift and charROM) to svn. Does it look right now? Yes, Curt, the ROM chars do look right. The change of the shift from ">> 5" to ">> 6" was right, but it comes out that more of MC6847's code still needs to be changed to behave properly. The most significative bit of the VRAM byte is lost somewhere, so only two colors are displayed twice, instead of four colors. Gotta check better to find what to change (without breaking what's working, glup).
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Joined: May 1999
Posts: 157
Senior Member
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Senior Member
Joined: May 1999
Posts: 157 |
Ah, I forgot to say... It's just the sample adventure given in the old Input Magazine. OMG! The Input Magazine!!! I still have the Italian edition at my parents' home... and this one too!
JoJo
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Joined: Jul 2009
Posts: 78
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OP
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Posts: 78 |
The change of the shift from ">> 5" to ">> 6" was right, but it comes out that more of MC6847's code still needs to be changed to behave properly. The most significative bit of the VRAM byte is lost somewhere, so only two colors are displayed twice, instead of four colors. Gotta check better to find what to change (without breaking what's working, glup). The Semigraphics 6 mode uses all of the bits of the byte read from the VRAM. Bits 7~6 code the foreground color; bits 5~0 code the block pattern. After trying to understand how m6847.c works, I guess that these changes would make Semigraphis 6 work correctly:
150 /* 2^7 modes, 256/16 character groups, background/foreground */
151 UINT8 colordata[128][256/16][2];
152
153 /* 2^7 modes, 256 characters, 12 scanlines */
154 UINT8 fontdata[128][256][12];
1200 bg_color = color(m6847->colordata[attr_index][byte / 16][0]);
1201 fg_color = color(m6847->colordata[attr_index][byte / 16][1]);
1210 char_data = m6847->fontdata[attr_index][byte][scanline % 12];
1798 for (byte = 0; byte < 256; byte++)
Try these, then type and run this BASIC program to see if there are four colors:
10 GR : OUT 128, 96
20 FOR A = 0 TO 255
30 POKE 32768 + A, A
40 NEXT
50 CALL 49158 : REM PRESS ANY KEY TO EXIT
60 TEXT
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Joined: Feb 2005
Posts: 449
Senior Member
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Senior Member
Joined: Feb 2005
Posts: 449 |
Yes, there is now in svn r5501:
green
yellow
blue
red
stripes on the screen with your changes.
I hope this doesn't break other drivers.
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Joined: Jul 2009
Posts: 78
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OP
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Joined: Jul 2009
Posts: 78 |
Yes, there is now in svn r5501: green, yellow, blue, red stripes on the screen with your changes.
I hope this doesn't break other drivers. Me too.  Only one thing, though: You forgot to change 128 into 256 in one comment line:
153 /* 2^7 modes, 128 characters, 12 scanlines */
154 UINT8 fontdata[128][256][12];
When the changes appear on the next BobZ Automatic Daily Build I'll check them out. _________________________________________________ Given that, let's check what's left at the TODO for MC-1000:
16 - cassette
17 - interrupt from NE555
18 - xtal frequency?
19 - Z80 wait at 0x0000-0x1fff when !hsync & !vsync
20 - MC6847 color artifacting is broken
21 - 80-column card (MC6845)
22 - Charlemagne / GEM-1000 / Junior Computer
- Cassette seems to be working right already.
- MC6847 does implement (NTSC) artifacts. Why you say it is broken? Because it doesn't implement PAL-M artifacts?
- Implementing Charlemagne/GEM-1000 depends on someone finding info on that obscure machine other than what's found in Old-Computers.com.
- As for MC6845 (80-column card)... In this case we would have the machine generating two screens simultaneously. How is this to be handled in M.E.S.S.?
- I'd need a longer description of the other TODOs.
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Joined: May 1999
Posts: 157
Senior Member
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Senior Member
Joined: May 1999
Posts: 157 |
- MC6847 does implement (NTSC) artifacts. Why you say it is broken? Because it doesn't implement PAL-M artifacts?
One of the (very) long-term goals of MAME/MESS is to implement artifacting at core level rather than at device level. I wonder if, given the specs of the three major standards (NTSC, PAL and SECAM) and the ITU id table, is possible to model (in a mathematical sense) all the possible artifact schemes. Of course, there will still be a little number of parameters that have to be tweaked by the user (gamma, tint, etc.) but it'd be funny to "connect" e.g. an Oric Atmos to a SECAM-M monitor and see what happens  - As for MC6845 (80-column card)... In this case we would have the machine generating two screens simultaneously. How is this to be handled in M.E.S.S.?
That's definitely easier to achieve: see the SVI-318 driver. Basically you plot the 32-columns display on screen #1, and the 80-columns display on screen #2: with the proper layout file you can display one of the two screens, or both, at your pleasure!
JoJo
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Joined: Feb 2005
Posts: 449
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Senior Member
Joined: Feb 2005
Posts: 449 |
[*]Cassette seems to be working right already. [*]MC6847 does implement (NTSC) artifacts. Why you say it is broken? Because it doesn't implement PAL-M artifacts? [*]Implementing Charlemagne/GEM-1000 depends on someone finding info on that obscure machine other than what's found in Old-Computers.com. [*]As for MC6845 (80-column card)... In this case we would have the machine generating two screens simultaneously. How is this to be handled in M.E.S.S.? [*]I'd need a longer description of the other TODOs. [/list] Cassette/MC6847 comments were obsolete, I removed them. Implementing the 80-column screen is trivial once we get a dump of the MC6845 character generator ROM. Or does it use video RAM instead?
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Joined: Jul 2009
Posts: 78
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Posts: 78 |
Implementing the 80-column screen is trivial once we get a dump of the MC6845 character generator ROM. Or does it use video RAM instead? Uh, I have no info on how MC-1000's 80-column capability was implemented.
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Joined: Jul 2009
Posts: 78
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Posts: 78 |
In order to check if the M.E.S.S. implementation of MC6847 was correct, I wrote a program in my MC-1000 ( .wav file) that draws the characters in Resolution Graphics 6 (two-color 256x192) mode (with data from one of the "fontdata" arrays found in file m6847.c) and other bytes so that, alternating between text mode and RG6 mode, the real characters and the characters drawn alternate in the same screen positions, so I could compare and easily perceive any misplaced or lacking pixels.
10 HGR
20 OUT 128,158
30 FOR A = 0 TO 511
40 POKE 32768 + A,32
50 NEXT
60 FOR A = 64 TO 127
70 POKE 32768 + A,A
80 FOR B = 3 TO 9
90 READ C
100 IF C THEN POKE 32768 + (A AND 224) * 12 + B * 32 + (A AND 31),C
110 NEXT B,A
120 OUT 128,1: FOR A = 1 TO 200: NEXT
130 OUT 128,159: FOR A = 1 TO 200: NEXT
140 GOTO 120
10000 REM DADOS DOS CARACTERES
10010 DATA 28,34,2,26,42,42,28
10020 DATA 8,20,34,34,62,34,34
10030 DATA 60,18,18,28,18,18,60
10040 DATA 28,34,32,32,32,34,28
10050 DATA 60,18,18,18,18,18,60
10060 DATA 62,32,32,60,32,32,62
10070 DATA 62,32,32,60,32,32,32
10080 DATA 30,32,32,38,34,34,30
10090 DATA 34,34,34,62,34,34,34
10100 DATA 28,8,8,8,8,8,28
10110 DATA 2,2,2,2,34,34,28
10120 DATA 34,36,40,48,40,36,34
10130 DATA 32,32,32,32,32,32,62
10140 DATA 34,54,42,42,34,34,34
10150 DATA 34,50,42,38,34,34,34
10160 DATA 62,34,34,34,34,34,62
10170 DATA 60,34,34,60,32,32,32
10180 DATA 28,34,34,34,42,36,26
10190 DATA 60,34,34,60,40,36,34
10200 DATA 28,34,16,8,4,34,28
10210 DATA 62,8,8,8,8,8,8
10220 DATA 34,34,34,34,34,34,28
10230 DATA 34,34,34,20,20,8,8
10240 DATA 34,34,34,42,42,54,34
10250 DATA 34,34,20,8,20,34,34
10260 DATA 34,34,20,8,8,8,8
10270 DATA 62,2,4,8,16,32,62
10280 DATA 56,32,32,32,32,32,56
10290 DATA 32,32,16,8,4,2,2
10300 DATA 14,2,2,2,2,2,14
10310 DATA 8,28,42,8,8,8,8
10320 DATA 0,8,16,62,16,8,0
10330 DATA 0,0,0,0,0,0,0
10340 DATA 8,8,8,8,8,0,8
10350 DATA 20,20,20,0,0,0,0
10360 DATA 20,20,54,0,54,20,20
10370 DATA 8,30,32,28,2,60,8
10380 DATA 50,50,4,8,16,38,38
10390 DATA 16,40,40,16,42,36,26
10400 DATA 24,24,24,0,0,0,0
10410 DATA 8,16,32,32,32,16,8
10420 DATA 8,4,2,2,2,4,8
10430 DATA 0,8,28,62,28,8,0
10440 DATA 0,8,8,62,8,8,0
10450 DATA 0,0,0,48,48,16,32
10460 DATA 0,0,0,62,0,0,0
10470 DATA 0,0,0,0,0,48,48
10480 DATA 2,2,4,8,16,32,32
10490 DATA 24,36,36,36,36,36,24
10500 DATA 8,24,8,8,8,8,28
10510 DATA 28,34,2,28,32,32,62
10520 DATA 28,34,2,12,2,34,28
10530 DATA 4,12,20,62,4,4,4
10540 DATA 62,32,60,2,2,34,28
10550 DATA 28,32,32,60,34,34,28
10560 DATA 62,2,4,8,16,32,32
10570 DATA 28,34,34,28,34,34,28
10580 DATA 28,34,34,30,2,2,28
10590 DATA 0,24,24,0,24,24,0
10600 DATA 24,24,0,24,24,8,16
10610 DATA 4,8,16,32,16,8,4
10620 DATA 0,0,62,0,62,0,0
10630 DATA 16,8,4,2,4,8,16
10640 DATA 24,36,4,8,8,0,8
Here I used black-and-white RG6. To avoid the resulting artifacting, I changed to black-and-green RG6:
130 OUT 128,157: FOR A = 1 TO 200: NEXT
Then I realized that NO CHANGE IN BACKGROUND COLOR is perceived.  Here's a video with the result: http://www.ensjo.net/mc-1000/MVI_1262.AVII have realized long before that black-and-green RG6's "black" background was somewhat greenish, but it never occurred to me that it was SO SIMILAR to text mode's dark green background. (Seemingly RG6's bright border gives us the impression that they are different.) Note that when we alternate between black-and-white and black-and-green RG6, we do perceive a change in background color: http://www.ensjo.net/mc-1000/MVI_1261.AVIThis having been said... QUESTIONS: Is this phenomenon observed in other machines based on MC6847? (A real TRS-80 Color Computer, for instance. Can anyone check it?) Is DARK GREEN the real background color of MC6847's black-and-green RG6 mode?
Last edited by Ensjo; 09/02/09 06:22 PM.
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