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PostPosted: Sat Aug 10, 2019 10:22 am 
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Joined: Sun Dec 24, 2017 10:16 am
Posts: 17
Hello,

We are trying to create a rom reader for SNES and have some issues. We are using pinouts informations from here :
https://www.caitsith2.com/snes/flashcar ... nouts.html

On snes maskrom, what is the goal of /OE (pin 31) and /CS (pin 22) ?
Do you confirm that :

- /CS means address is ready for SNES ?
- /OE byte is ready for ROM ?

Do you know if value is ready when /CS has HIGH or LOW value ? We think it is ready when value is LOW

When we log informations, we see a lot of adress and values but nothing appear to the screen. Do you have any idea what could be the issue ?
Is it normal that address 80068 appears a lot of times ?
Here is a log we get after few seconds :

Adress and data value: 32238 - 107
Adress and data value: 65406 - 255
Adress and data value: 65422 - 255
Adress and data value: 32735 - 234
Adress and data value: 61299 - 48
Adress and data value: 31630 - 240
Adress and data value: 31695 - 5
Adress and data value: 22511 - 38
Adress and data value: 63487 - 35
Adress and data value: 28415 - 2
Adress and data value: 53246 - 0
Adress and data value: 65535 - 255
Adress and data value: 31707 - 116
Adress and data value: 64477 - 46
Adress and data value: 1856 - 169
Adress and data value: 17226 - 0
Adress and data value: 27353 - 252
Adress and data value: 65391 - 255
Adress and data value: 65386 - 255
Adress and data value: 30699 - 34
Adress and data value: 59982 - 4
Adress and data value: 28671 - 0
Adress and data value: 54987 - 0
Adress and data value: 17218 - 133
Adress and data value: 52062 - 255
Adress and data value: 30450 - 169
Adress and data value: 63340 - 35
Adress and data value: 36723 - 1
Adress and data value: 60379 - 0
Adress and data value: 60271 - 32
Adress and data value: 27483 - 52
Adress and data value: 61266 - 242
Adress and data value: 63307 - 0
Adress and data value: 63199 - 229
Adress and data value: 17226 - 0
Adress and data value: 27358 - 248
Adress and data value: 31476 - 116
Adress and data value: 60234 - 9
Adress and data value: 64367 - 0
Adress and data value: 27507 - 2
Adress and data value: 31739 - 128
Adress and data value: 31699 - 76
Adress and data value: 65151 - 255
Adress and data value: 46911 - 31
Adress and data value: 63227 - 34
Adress and data value: 27507 - 2
Adress and data value: 31575 - 255
Adress and data value: 60239 - 34
Adress and data value: 367 - 74
Adress and data value: 80068 - 22
Adress and data value: 96980 - 0
Adress and data value: 97429 - 0
Adress and data value: 96668 - 47
Adress and data value: 95231 - 2
Adress and data value: 97014 - 0
Adress and data value: 113364 - 176
Adress and data value: 96991 - 16
Adress and data value: 97525 - 76
Adress and data value: 71876 - 149
Adress and data value: 113369 - 5
Adress and data value: 80606 - 11
Adress and data value: 114421 - 240
Adress and data value: 81141 - 159
Adress and data value: 130972 - 255
Adress and data value: 97148 - 10
Adress and data value: 92822 - 68
Adress and data value: 113365 - 2
Adress and data value: 95660 - 48
Adress and data value: 112938 - 134
Adress and data value: 80757 - 166
Adress and data value: 97774 - 28
Adress and data value: 80068 - 22
Adress and data value: 129630 - 206
Adress and data value: 113391 - 73
Adress and data value: 130777 - 14
Adress and data value: 130801 - 165
Adress and data value: 80068 - 22
Adress and data value: 80064 - 76
Adress and data value: 92373 - 14
Adress and data value: 129774 - 128
Adress and data value: 80068 - 22
Adress and data value: 80068 - 22
Adress and data value: 122081 - 144
Adress and data value: 75972 - 201
Adress and data value: 81215 - 159
Adress and data value: 79876 - 240
Adress and data value: 89246 - 201
Adress and data value: 97229 - 194
Adress and data value: 80068 - 22
Adress and data value: 80068 - 22
Adress and data value: 121193 - 173
Adress and data value: 128409 - 224
Adress and data value: 80068 - 22
Adress and data value: 80068 - 22
Adress and data value: 97641 - 26
Adress and data value: 88937 - 107
Adress and data value: 97769 - 9
Adress and data value: 80068 - 22
Adress and data value: 95092 - 171
Adress and data value: 80068 - 22
Adress and data value: 88437 - 196
Adress and data value: 73142 - 176
Adress and data value: 120171 - 0
Adress and data value: 126420 - 201
Adress and data value: 113524 - 149
Adress and data value: 80064 - 76
Adress and data value: 122236 - 18
Adress and data value: 80068 - 22
Adress and data value: 97770 - 201
Adress and data value: 80068 - 22
Adress and data value: 71876 - 149
Adress and data value: 80281 - 185
Adress and data value: 130009 - 232
Adress and data value: 80068 - 22
Adress and data value: 80686 - 107
Adress and data value: 80068 - 22
Adress and data value: 96502 - 16
Adress and data value: 78453 - 0
Adress and data value: 103657 - 74
Adress and data value: 75908 - 34
Adress and data value: 118681 - 60
Adress and data value: 98206 - 169
Adress and data value: 78020 - 152
Adress and data value: 118734 - 56
Adress and data value: 71876 - 149
Adress and data value: 80068 - 22
Adress and data value: 114138 - 144
Adress and data value: 80068 - 22
Adress and data value: 110038 - 50
Adress and data value: 80068 - 22
Adress and data value: 80068 - 22
Adress and data value: 74511 - 169
Adress and data value: 75844 - 2
Adress and data value: 80064 - 76
Adress and data value: 110062 - 153
Adress and data value: 114073 - 133
Adress and data value: 130423 - 6
Adress and data value: 75972 - 201
Adress and data value: 119777 - 30
Adress and data value: 80068 - 22
Adress and data value: 113631 - 181
Adress and data value: 114026 - 25
Adress and data value: 81401 - 10
Adress and data value: 93561 - 34
Adress and data value: 113385 - 10
Adress and data value: 98024 - 34
Adress and data value: 80484 - 41
Adress and data value: 80068 - 22
Adress and data value: 109284 - 169
Adress and data value: 80068 - 22
Adress and data value: 80000 - 0
Adress and data value: 80068 - 22
Adress and data value: 88542 - 50
Adress and data value: 78020 - 152
Adress and data value: 78441 - 0
Adress and data value: 106390 - 208
Adress and data value: 96745 - 3
Adress and data value: 80068 - 22
Adress and data value: 89054 - 30
Adress and data value: 130462 - 28
Adress and data value: 80068 - 22
Adress and data value: 71876 - 149
Adress and data value: 118553 - 207
Adress and data value: 109927 - 54
Adress and data value: 88814 - 149
Adress and data value: 125289 - 194
Adress and data value: 89853 - 26
Adress and data value: 79940 - 26
Adress and data value: 80068 - 22
Adress and data value: 113001 - 0
Adress and data value: 129679 - 0
Adress and data value: 125289 - 194
Adress and data value: 88805 - 40
Adress and data value: 80281 - 185



Thanks for your help


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PostPosted: Sat Aug 10, 2019 11:54 am 
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Joined: Sun Apr 13, 2008 11:12 am
Posts: 8539
Location: Seattle
On the physical ROM, /CE and /OE are signals that respectively power up the matrix of bits inside, and drive the contents of the powered-up matrix onto the data bus.

On the SNES cartridge connector, pin 49 ('/ROMSEL') is low if
A15 is high or A22 is high
and A23 downto A17 is not b'0111111'

The SNES is an asynchronous device, and there is no "address ready" signal.


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PostPosted: Sun Aug 11, 2019 11:39 am 
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Joined: Fri Feb 24, 2012 12:09 pm
Posts: 975
hoit wrote:
Here is a log we get after few seconds :
Adress and data value: 32238 - 107
Adress and data value: 65406 - 255
Adress and data value: 65422 - 255
Adress and data value: 32735 - 234
Adress and data value: 61299 - 48
Adress and data value: 31630 - 240
Adress and data value: 31695 - 5

I don't what you have logged there and why. If you store the ROM-image in a SRAM, then the SRAM should handle all memory accesses by itself, and there is no point in (trying to) log that accesses. What I can say is that the log is huge failure : )
First of, if you were intersted in the log values, then you would show them in hexadecimal, and compare them with bytes and addresses in the ROM-image disassembly.
Even with the decimal values, it looks obvious that the values are random, without any opcode fetches from increasing addresses.
It may be also goot to start logging at the rom entrypoint, not after a few seconds.

lidnariq wrote:
The SNES is an asynchronous device, and there is no "address ready" signal.

What is with the CPU_CLK edges? I guess they could serve as "address ready".
I am not sure, they might also serve as "address is ready, and data must be ready, too".
The latter might be useful when logging address+data from an already existing & working memory chip.
But it might be not useful when trying to emulate a memory chip.

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