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#1
avatar_TheElectricMonk
Programming / Re: 8BP
Last post by TheElectricMonk - Today at 14:29
Private message sent, let me know if you got it  :)
#2
Check the flat cable to the drive. You removed it to replace the belt and it may have loosened some wires. Also check the drive PCB (especially the sockets) for dry joints.

Bryce.
#3
I'm just getting back onto this today, I think the first step will be desoldering the ROM and checking it out making use of the TL866II+. I have one more 28 pin socket left so I'll have the board ready for a replacement or returning the original back if all looks good there 
#4
avatar_roudoudou
Amstrad CPC hardware / Re: Memory refresh plus
Last post by roudoudou - Today at 12:53
Quote from: djaybee on Today at 11:09Note that some interrupt code runs every 52 lines, which also causes some refresh.

Quasar CPC was talking about the refresh bug on the Plus, mixing line-per-line split and PRI (you set a raster line interrupt which never occurs). i didn't digged that part but it's a lead

#5
avatar_McArti0
Amstrad CPC hardware / Re: Memory refresh plus
Last post by McArti0 - Today at 12:41
Exactly this month, I embarrassed myself on the forum regarding this issue.   :laugh:

CRTC is not refreshing CPC only when R0=0. if R0<>0 then CRTC counters always work and refreshing (at border too)
#6
OK the FDC status is being returned, so the FDC and associated select logic is probably OK. I would run the Diagnostics ROM and see if the AMSDOS checksum is ok.
#7
F
Games / Re: B.A.T. English working?
Last post by flolore - Today at 11:17
On the first sreen, you have a choice to do, "creator" or"play", i have selecting "play" with the joystick, and fire to load the game. After one second, i insert the disk 2 on demand, and the first game's screen is loaded with the train in the station.

After few tests, there are an issue with this dumb, you are right, but i haven't had this bug the first time. If you load the "creator" part in first and back on the first screen in next to load the "play" part, so the game is running, but if you load the "play" part directly without to load the "creator" part in first, so that kill the emulator directly, back to windows... so this dumb (disk 2) isn't perfect as i thought.

PS hehe yes for the joystick input, but you're not totally wrong ;)
#8
D
Amstrad CPC hardware / Re: Memory refresh plus
Last post by djaybee - Today at 11:09
Reviving an ancient thread, because I was curious about the same thing. I suspect that the CRTC 6845 keeps generating MA addresses throughout the line (and probably the whole frame), and merely resets them at character 0. This is based on the Motorola 6845 manual, figure 12, which shows MA addresses on the address bus even when DISPEN is off.

Combining that with the layout of R and C lines to the DRAM, that implies that the CRTC needs to hit 512 consecutive words (256 CRTC characters) within 2ms (the max allowed refresh period for the 4164B-15 DRAM, from the datasheet). 2ms is about 31 lines at 64us.

A standard display with 40 CRTC characters actually needs 41 lines to hit that many characters (64 characters per line, which increments by 40 every 8 lines). That slightly off-spec, but not by much.

Reduced-width displays might be worse. A 32-character-wide "speccy" display will need 49 lines, i.e. about 50% longer than spec. Narrower screens get worse, e.g. a 24-character display takes 65 lines, more than double the specified time, and so on.

Note that some interrupt code runs every 52 lines, which also causes some refresh.

From there, I'll guess that preventing some of the RAM from getting refreshed might require to use a very narrow display to reduce the address increment from character row to character row. Things might get worse if the display is very tall (it's hard to guess what happens during the top/bottom borders), and you can worsen things by a few DRAM rows if you use very tall CRTC characters. Obviously, your Z80 has to stay within the DRAM rows that get hit by the CRTC on each line, so that it doesn't cause the other rows to get refreshed. That requires that interrupts be disabled.

Not knowing for sure what addresses get generated during the top/bottom border, you might not be able to disable refreshes in some areas for more than about 296 lines, i.e. not forever, though it'd be interesting to investigate what happens if you make the display 312 lines tall (R6 = 39 with the default R9).

I don't have an actual CPC to test that on. Nor do I have an appropriate oscilloscope or logic analyzer to investigate the pin-level details if I had a CPC (an oscilloscope on the CRTC's MA7 pin might be enough).
#9
avatar_Gryzor
Games / Re: B.A.T. English working?
Last post by Gryzor - Today at 11:01
Quote from: flolore on Today at 10:47Hi,

This dump is perfect, i have trying with the caprice32 emulator (https://github.com/ColinPitrat/caprice32) and all is good, maybe you have a problem with your emulator...

Good play ;)

Well, it's the same with this one... what do you do once the loading screen is displayed?

Ah darn it just needs joystick input :D
#10
F
Games / Re: B.A.T. English working?
Last post by flolore - Today at 10:47
Hi,

This dump is perfect, i have trying with the caprice32 emulator (https://github.com/ColinPitrat/caprice32) and all is good, maybe you have a problem with your emulator...

Good play ;)
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