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Post Info TOPIC: Yoshbox (Serial EPROM) control logic...


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Yoshbox (Serial EPROM) control logic...


Have been asked to look into if it is possible to remove Yoshbox effects from the reflashed ecu:s. As many of the bikes who come for reflashing with a yoshbox tune, the standard maps can not be easily used.

Therefore an idea about modifying the ECU code so that yoshbox stored value information is disabled after reflashing the ecu.

So if any of the readers know how to locate the Serial EPROM controlling code and have any ideas about disabling ( have fixed values for Yoshbox stored maps) - would appreciate.

From hardware disassembly I vaguely recall that the yoshbox is programming is held in the serial EPROM which is connected to TxD2 and RxD2.


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The way the ZX-12 and older 16 bit busa used these values was that at reset all the Yosh values were copied from the serial eeprom into RAM and it is the actual RAM values that are used by the injector subroutines.

Instead of hunting down everywhere these values are used and modifying all of those areas I think it would be easier to modify the start up routine to just copy  0x80s into all the ram locations  (0x80 is midpoint no change. Above 80 fuel is added, below 80 fuel is reduced)

Also I don't know about the busa but the zx12 has a yoshbox setting that causes the software to reset all the yosh values to midpoint. So you may be able to 'zero' the yosh values once using some resistors and not have to worry about it again.

It's hard to say which would be quicker, tracking down the yosh reset values or finding the value copy routine and altering it.

I will look up the relevant addresses for the routines I know of later today.

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RR, that would be superb. I think the place to look into is:

ROM:00004C80 Unsure_read_serial_eprom_sub_4C80:

But unfortunately that piece of code goes a bit over my head without some intense concentration to risc. I ended up there using this route:

COV3 AD: FFFF81DA -> FFFF8377 -> FFFF83CD
->
ROM:0000DBC4 unsure_yoshbox_COV_setting_FFFF8528_sub_DBC4
->
ROM:00004C9C loc_4C9C:
->
ROM:00004C80 Unsure_read_serial_eprom_sub_4C80:


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I only have experience with the Nikko box (a copy of the Yosh box).

According to its instructions, for the low load, individual cylinder setting you can reset the factory defaults by setting the potentiometer to either of the limits (0 or 5 V).

For the high load adjustment it has discrete switch settings, so using the zero setting should be close enough.

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Hi Motty, Yes - its easy if you still have the Yoshbox device available and wires attached.

Anyhow the wiring instructions advice to relocate the yoshbox wires so we really should look into disabling the yoshbox code - particularly as we all dont have access to yoshbox.

Need to look into the disasm and hope that RR can figure out also something...



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Maybe its indeed easier to hack the contents of the variables used in fuel calculations, e.g. 8510,8511,...

0000F878 Calculate_Cylinder0_FFFF84A6_FFFF849E_sub_F878:
ROM:0000F878 ; CODE XREF: Calculate_Limiters_Maps_and_Timers_sub_E24C+456Cp
ROM:0000F878 ; DATA XREF: ROM:off_128D4o
ROM:0000F878 mov.l r14, @-r15
ROM:0000F87A sts.l pr, @-r15
ROM:0000F87C mov.l @(h'138,pc), r2 ; [0000F9B8] = h'FFFF8510 ; Cov 3
ROM:0000F87E add #-8, r15
ROM:0000F880 mov.l @(h'138,pc), r1 ; [0000F9BC] = h'FFFF854E ; Fuelcut map multiplier
ROM:0000F882 mov.b @r2, r3
ROM:0000F884 mov.l @(h'138,pc), r0 ; [0000F9C0] = h'FFFF84B6 ; IAP Fuel Map compensation value
ROM:0000F886 mov.b r3, @r15
ROM:0000F888 mov.b @r1, r14
ROM:0000F88A mov.b @r15, r4
ROM:0000F88C extu.b r4, r4
ROM:0000F88E add #-h'80, r4 ; (Cov3 - 0x80) * 4
ROM:0000F890 shll2 r4 ; *4
ROM:0000F892 mov.l r4, @(4,r15)


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I suppose you could change all the code that points to RAM addresses h'FFFF8510 etc point to the same map address in flash which you set to h'80 (no change). That would just be a simple byte rewrite like map values and not require compiling the code or anything like that.

There also is sub_E984 which sets all those values to h'80 as part of a general memory initialization. If you called it a second time after the ram was loaded from the serial eeprom it would set it back to no change. The trick of course is figuring out where to to stick the second call.



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Petrik did you make any progress on resetting yoshbox value, i have two ecu i bought that has hard starting issues it turns out that they were tune with the yoshbox, Daveo suggested that i change them out, because he has seen that happen in the past when the ecu were tune with the yoshbox. now bike starts up just fine, before it would turn over and over before it would fire.. 



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Sorry - have not had time. Just got my Yoshbox back, but its not yet wired up to the ecu on the desktop. When I have time this is on the list... after some more code reading its just simple test and verify excercise. But B4 hardware is wired up its not gonna be easy.

Often RR can suggest some ideas that are really close or even exact solutions - so I hope to hear more of him too...

Anyway this is a common issue for all of us.

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