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1 user currently in Rom Hacking:  hukka |
| Acmlm's Board - I2 Archive - Rom Hacking - Editing code after tracing it |
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Ringodoggie Snifit Level: 27  Posts: 222/281 EXP: 114340 For next: 1819 Since: 03-23-04 From: London, Ontario, Canada Since last post: 27 days Last activity: 5 hours |
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| In SNES9x Debug, how do I edit code that I trace? Do I disassemble the ROM first? | |||
beneficii Lakitu Level: 36 Posts: 239/567 EXP: 299656 For next: 8454 Since: 06-27-04 From: Cordova, TN, USA Since last post: 14 hours Last activity: 6 hours |
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| In FCEUXD, when I trace it, I look through the code I know I'll be editing and plan for what I'll be doing. I then open up Notepad to type my new ASM. Then I open up the ROM in a hex editor and write in the opcodes myself. | |||
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Ringodoggie Snifit Level: 27 Posts: 224/281 EXP: 114340 For next: 1819 Since: 03-23-04 From: London, Ontario, Canada Since last post: 27 days Last activity: 5 hours |
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| What about DMA code? (edited by Ringodoggie on 07-05-05 01:27 PM) |
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beneficii Lakitu Level: 36 Posts: 240/567 EXP: 299656 For next: 8454 Since: 06-27-04 From: Cordova, TN, USA Since last post: 14 hours Last activity: 6 hours |
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Originally posted by Ringodoggie Do you mean sprite-loading code? Remember, I only really know the NES, not the SNES. I was just dropping off advice I thought was general ASM hacking. |
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d4s Panser Level: 29  Posts: 245/325 EXP: 142151 For next: 5734 Since: 03-23-04 Since last post: 13 days Last activity: 1 day |
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Originally posted by beneficii manually compiling code is a big time waster and doesnt give you any advantages at all. ive done it myself, but only for processors that dont have a compiler available (super fx) and only for very, very small amounts of code, like 3 to 4 opcodes. besides, its nearly impossible to write proper structured and dynamic code that way. why not use wla dx or any other readily-available compiler instead? Originally posted by Ringodoggie i assume you want to either detect dma transfers or you want to learn how to do them the right way. try to be more specific with your questions. |
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Ringodoggie Snifit Level: 27 Posts: 226/281 EXP: 114340 For next: 1819 Since: 03-23-04 From: London, Ontario, Canada Since last post: 27 days Last activity: 5 hours |
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| I mean how do I change an address that is DMA'd to? | |||
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beneficii Lakitu Level: 36 Posts: 241/567 EXP: 299656 For next: 8454 Since: 06-27-04 From: Cordova, TN, USA Since last post: 14 hours Last activity: 6 hours |
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| Probably because I don't trust those programs to write the code into, say, SMB3 the right way, so I simply do it myself. Now, if I was writing a ROM from scratch, then I would definitely use an assembler. Originally posted by d4sOriginally posted by beneficii |
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BGNG Snifit Level: 22  Posts: 120/276 EXP: 56579 For next: 1771 Since: 06-03-05 Since last post: 8 days Last activity: 3 hours |
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| You might be able to find some useful info by looking up some technical documentation on the subject. Not exactly "change the programming"-esque, but it may provide some useful insight. (edited by BGNG on 07-05-05 02:55 PM) (edited by BGNG on 07-05-05 03:02 PM) |
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d4s Panser Level: 29 Posts: 246/325 EXP: 142151 For next: 5734 Since: 03-23-04 Since last post: 13 days Last activity: 1 day |
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Originally posted by Ringodoggie a dma transfer is initiated by writing to register $420B. the individual bits correspond to the dma channels(0-7), eg writing $01 to $420b will start a dma transfer on channel 0, $06 will start transfers on channels 1 and 2, you get the idea. each dma channel is configured by writing to registers $43x0-$43x7 (x is the channel number). the relevant registers for changing the dma transfer source are $43x2-$43x4 (source adress+bank). example: if theres a dma transfer on channel 2 and you want to change the source adress to $c6:0388 you'd have to write $0388 to register $4322 and $c6 to register $4324. keep in mind that hdma and dma share the same channels when adding/changing dma transfer channels. you can only dma from the a-bus to the b-bus (thats the ppu registers) or vice versa, but not from a to a or from b to b, mind you. that means you can dma from rom to vram, but not from rom to wram, for example. register $43x1 determines the b-bus target adress. when writing to vram, it is used in conjunction with register $2116, wich contains the vram target adress. keep in mind that vram adresses are always divided by 2 because theyre 16bit aligned. heres how a typical dma transfer looks like: ;********************************** ;in: x,16bit: pointernumber of tilemap ;********************************** CGIntroDMATileMapToVramBG2: sep #$20 lda #(:BG2TileMap1+$c0) ;get source bank of tilemaps sta.w $4304 ;Store the bank of the source data rep #$30 ;accu/index 16bit txa ;get number of tilemap asl ;multiply by 4(each table-entry has 2 bytes adress, 2 bytes length) asl ; tax lda.w Bg2TileMapPTable,x ;get source offset of tilemap sta.w $4302 ldx.w #$0800 stx.w $2116 ;vram adress $0000 lda.w #$1000 sta.w $4305 ;Store the size of the data block sep #$20 lda #$80 sta $2115 ;set VRAM transfer mode to word-access, increment by 1 lda #$01 ;Set the DMA mode (word, normal increment) sta $4300 lda #$18 ;Set the destination register (VRAM gate) sta $4301 lda #$01 ;Initiate the DMA transfer sta $420B rts |
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