VVVVVV for MSX | MSX Resource Center (Pagina 7/8)

Prophet (2932)

29-09-2012, 19:07

With OUTI and INI, their header cycles are not clear.
I.e. it is not clear in which cycle they go on the IO port.
But with the two opcodes it got to be at least 10 cycles:

;for MSX2
;putting VDP in read mode
out (c),l
out (c),h
--- start counting here
8 add 0
10(+x) ini
--
18

In this INI example, the "use 7 cycles padding" rule maybe wrecks, got to be 8 padding cycles.

Using two times the same instruction, things are clear,
time from IO acess to IO acess got to be 18 cycles.
outi
18 outi

NOTE the examples were just about how to do cycle counting,
I feel one should leave it with

;for MSX2
;putting VDP in read mode
out (c),l
out (c),h
nop
nop
INI

or

;for MSX2
;putting VDP in read mode
out (c),l
out (c),h
nop
nop
nop
IN (0x98),a

(different padding because a faster IO instruction follows)

disclaimer. All this is not based on tests on the real machine, just working with the VDP model.

Van sd_snatcher

Prophet (3675)

29-09-2012, 19:28

@hit9918

The Sony MSX2+ machines use the standard V9958 VDP. The Z80A is also a standard Zilog. But many programmers forget that those things need to communicate through that subtle thing called motherboard.

On this case, the limitation relies on the motherboard: they took some design decisions that limited the communication speed on the tracks that go from the VDP to the VRAM. That, added to a bug present on the S1985, restricts speed. But as the achievable speed was still within the spec limits, they didn't bother to add costs to improve it.

It is possible to upgrade this with some minor mods, and indeed I already did this mods on my HB-F1XDJ. But the vast majority of Sony MSX2+ machines will certainly be original.

I don't know if this restriction also affects the Sony MSX2 machines like the HB-F1XD.

Van hit9918

Prophet (2932)

30-09-2012, 16:00

@sd_snatcher, often the problem is lack of documentation.
The standard is a puzzle

Been playing with slots these days, an example, ENASLT lacks documentation!
It is missing the documentation whether it does update SLTTBL and whether its operation does depend on these bytes.
SLTTBL is documented API, so this would need to be mentioned. It is like not mentioning all call parameters / return values.

About the slow VDP, a problem between VDP and vram, how is that possible? The display 256x212 60 times per second means above 3 megabytes per second, a magnitude higher than cpu transfer! A problem in that area, the display would have to break down. The TMS always been on separate vram, who else should be in between?

Van sd_snatcher

Prophet (3675)

30-09-2012, 20:51

You're right it's hard to find a complete documentation for MSX programming in English. The MSX1 is pretty well documented, but when it comes to MSX2/2+/Turbo-R the English documentation was diminishing for each generation.

Those are some of the best documentation you can have:

MSX1:
- The MSX Red Book:
Advantages: Very detailed information on all MSX1 BIOS functions and on the hardware.
Disadvantages: Covers only the barebones MSX1, lacks DiskBIOS, DOS and EXTBIO information. It focus on being descriptive, thus lacks information on coding guidelines and examples. Lacks information for hardware developers. Lacks BASIC programming documentation.
- The MSX Technical Handbook
Advantages: Good source of information on the MSX standard. Contains many recommendations on coding guidelines, with sample code. Very detailed information for hardware developers.
Disadvantages: Could have more information on the BIOS calls. Lacks DOS programming information.

MSX2:
- MSX2 Technical Handbook

All generations
- MSX Datapack
Advantages: Covers all the MSX standard generations, all extensions, all hardware, BASIC, guidelines etc.
Disadvantages: Available only in japanese
- MSX Assembly Page
Advantages: Offers a lot of good information and programming tips on the Resources and Articles session. Unique source of information on VDP glitches and how to code a proper splitscreen, etc. Very good BIOS/SubROM call list. Excellent MSX-DOS2 programming documentation.
Disadvantages: BIOS/SubROM call list lacks information on when DI/EI state is changed. Most sample code don't follow the MSX coding guidelines. Lacks documentation on extension BIOSes, like DiskBIOS, RS232, MSX-Music, MSX-Audio etc.

I hope this list help you on your MSX programming.

Van sd_snatcher

Prophet (3675)

26-10-2013, 16:04

Any news about this project?

Quote:

About the slow VDP, a problem between VDP and vram, how is that possible? The display 256x212 60 times per second means above 3 megabytes per second, a magnitude higher than cpu transfer! A problem in that area, the display would have to break down. The TMS always been on separate vram, who else should be in between?

It seems that when you write too fast to the VDP on the HB-F1XDJ & F1XV, the [url=http://en.wikipedia.org/wiki/Ringing_(signal)]ringing effect[/url] shows up in the control lines that connect the VDP to the VRAM. In order to save costs, Sony omitted some resistors that could have avoided the problem, probably because without such resistors the machine would still fit inside the standard speed specs.

Van mars2000you

Enlighted (6555)

26-10-2013, 16:25

hap wrote:

VVVVVV for MSX, (C) hap, (C) Terry Cavanagh
I haven't worked on it for almost a year, I hope it won't become vaporware
free WIP version, 08-2012 public release, but please do not redistribute!
16KB RAM, MSX1 or 2, meant to play on 60hz/ntsc
128KB ROM, ascii8 or konami scc, no sound
cursor keys to move, sorry no joystick support

some parts of the game are playable, levels are not yet finished though
hold [1] key at boot: start at first level
hold [2] key at boot: start at trampoline level
hold [3] key at boot: start at conveyor level
hold [4] key at boot: start at autoscroll level
hold [5] key at boot: play with your willy

have fun, fail often