Radica Sega Genesis 6 in 1 "Hacking"

[oompa loompa]

Finally got myself a Sega Genesis Radica =P, the volume 1 type with the sonic the hedghog and flicky and stuff. Well, i really didn't want to rip it all apart yet because i plan to do something else with the 6 in 1 later. Here are some things that i poked around at:

the circuit on the back side of the board (the side without the glob top chips) is a banking circuit. it looks like radica didn't want to recompile sources to reallocate the gaming codes, so they made a simple OR bank switcher. what this bank switcher does is take the upper addresses and block them with a high level if a latch is on, or buffer the signal when the latch is off.

devster.retrodev.com/pub/radica_banking.gif

Here's the joypad color codes:
Brown - SEL
Red - B/A
Orange - UP
Yellow - DOWN
Green - LEFT/0
Blue - RIGHT/0
Purple - C/START
Gray - +3.3V
Black - GND
White - !RESET

The joypad connections follow the usual 74ls157 data selector convention

I've also found the cpu clock signals and some test points, i'll post more info on these later. if anyone would like to add anything to this, feel free =D, i dunno how much "hacking" has been done on the radica by others yet. i'll get to desoldering the mask rom board, and dissassembling the source later

[Kaneda]

well...All i know is the Portable Genesis projet and how to connect any cart to the radica (and so have an ultra small Genny)

thanks anyway for all these infos..it's better than "put a wire here and here and play"

[Tom Maneiro]

Do you mean... the Sega Exodus?

[oompa loompa]

oh yea, the exodus, i remember now, people were on these boards trying to get help on to figure out the pinouts for the rom =P. at that time, if i knew exactly were the gnd and vcc lines went, i would have automatically said it was the standard 16 bit mask rom pinout =D. maybe if i were to look more on the net, i'd find more info myself .

still haven't desoldered the mask rom yet, waiting for summer so i could start on this project =P

[oompa loompa]

hehe, dunno how to say this in one word, but i've done lots of work on the radica today =D, hacking it inside-out. things done:

1) desoldered the board holding the glue rom
2) soldered the rom to an empty cartridge and hooked up dip switches for the banking
3) dumped the rom onto hard drive
4) dissassembled rom source
5) solder on a connector onto the radica, much like my "sega genesis 50 pin bus"
6) ran games and test programs on the radica

all this was done in complete succession , so got lots done quickly today =P. i'll have the rom dump, dissassemblies, hardware notes, etc whenever i get to it

[Kaneda]

hehe!! I'm waiting for it!!

I hope you'll do the same thing with the 2 players versions coming soon

[oompa loompa]

hehe, i don't see anything the original radica already does that the street fighter one will do, except for the extra 2 player port =P (can't find any traces that are for the second port). a 6 button controller can already be interfaced to the radica. it also has write signals, so games with backup sram can be used ;D

i also have the menu running in emulators too =D

[Tom Maneiro]

any ROM release?

anyway, the menu runs, but.. can any game be loaded? Or it needs to emulate a custom mapper? (like Realtec crap gamez that need to be tricked with cheat codes)

[paulpsomiadis]

@oompaloompa - could you create a wiring diagram to show how to add the dipswitches...

I put the Rom from my Radica into a cart, but didn't know about the dipswitches so I can't get it to work on a real Genny!

Also, when you dumped the ROM - did you dump the entire thing or did you have to use the bank switching on the cart to dump ROM 'parts' in succession?

[paulpsomiadis]

ME AGAIN! (yah, I know I should create an account - maybe for my next post...)

Okay so...from what I understand...

@oompa loompa - your schematic shows that the Radica uses one 74LS174 and two 74LS32 chips for it's bank switching...

...in theory, could this allow someone to bank switch on a REAL Genny using the controller to select games like on the Radica...or would the DIP switches still be necessary?

[oompa loompa]

yay, i didn't know there'd be many people interested in the radica =P. anyways, i don't have a lot of time to respond since i'm in a rush

i'll upload the menu portion of the rom later. don't want to put the whole 4mbyte rom on cause it eats bandwidth =), and most importantly - the games that are on the radica are the exact same copies of the games that are in their respected individual cartridges (except for kid chameleon). the menu rom does not run on real hardware, but for some reason will run on emulators

as for the bank switching, there are no emulators that emulate this. to connect dip switches to act as a manual bank switcher, you will need to connect one pin of a SPST switch directly to the rom. You will also need to connect this pin to a pull-up resistor so the pin stays in logic high when the switch is open. On the other poll of the switch, connect this pin to the cartrdige address that matches the address line of the rom. do this for the top 6 address lines. look at the bank switching schematic for automatic switching to verify everything.

i think i described the banking mechanism already. when the latch is logic high, the address stays logic high. when the latch is logic low, the address follows the address line that is fed into the or-gate. knowing this, you can connect a dip switch different to what i've described above also =)

when i dumped the rom, i dumped the entire rom with the switches on, so that addresses are fed directly to the rom instead of making it "dominantly" high

the banking latch in the schematic latches data when some funky address $A13xxx i think is put on the bus, only on the radica hardware. on the original genesis, there are no signals that tell us when this space is being accessed. to make switching automatic, there would need to be extra logic to detect for this address space so that the menu program can write to the latch appropriately. i have not gotten the menu program to run on real hardware yet, and have not figured out why it locks up, so using automatic switching like on the radica is going to take more work than it really is worth. using the dip switches, kid chameleon does not work because the initial vector program counter is changed to jump to the menu code (see the memory map on the schematic, kid chameleon is put at the begining of the rom, and the vector table is located at the begining of the rom so something needs to be done so that when the radica is turned on, kid chameleon isn't immediately played)

also, i got an email asking about region detection =). i guess there's been lots of talk about whether the radica has region detection or not, and why many games don't run, and people are thinking its region detection but don't really know the answer. the real answer is that the radica does include the region code, and that region code is the same as the sega genesis model 1, version 2 system =D. for experts, this region code in $A10001 reports as $A1 =P (look in sega docs for what this means)

any other questions i'm willing to ask later, don't be afraid to ask because i spend more time answering questions on the forum rather than making documents =P

[paulpsomiadis]

Hmm...let me get this straight...(using ASCII art!) ;D

--
|A16---|---./ .---1
R |A17---|---./ .---2
O |A18---|---./ .---3
M |A19---|---./ .---4
|A20---|---./ .---5
|A21---|---./ .---6
-- |
|
R1
|
|
VCC CART PIN

Points 1-6 = A16-A21 at base of cart

Okay Q/A again...

1. What resistor value do you recommend?

2. So ALL of the pins are constant logic HIGH, unless switched to their respective cart pins...correct?

Finally...

3. Which 'test points' did you find (a picture with red labels would be useful) and did you find a way of doing the overclock 'hack'...i.e. - a test point for the 13MHz signal and a way to send a halt signal between switching?

[paulpsomiadis]

GRR...my ASCII art got FUBAR 'cos the forum removes spaces!

I'll try once more...(the @ signs are 'invisible'...LOL! ;D)

--
@|A16---|---./ .---1
R |A17---|---./ .---2
O |A18---|---./ .---3
M |A19---|---./ .---4
@|A20---|---./ .---5
@|A21---|---./ .---6
--@@@@|
@@@@@|
@@@@@r1
@@@@@|
@@@@@|
@@vcc CART PIN

[oompa loompa]

uhm, the ascii art suxorz =P. also each signal needs an individual resistor of its own so that each signal is not tied together, and the flow of current isn't divided. i just quickly made a schematic for the switches, and you can find it here devster.retrodev.com/pub/radicav1manualbankswitch.gif. i used the usual 10k pull ups, but something between 4.7k and 10k is good. you can also connect the signal to your 3.3v reference, but this is where you'll need a smaller resistor value

the menu dump portion of the rom can be found here: devster.retrodev.com/pub/radicav1_menu_dump.bin

i uploaded the entire 4mbyte rom at eidolons-inn, so tell all your friends =o! you can find it in the file manager under genesis dev

EDIT: notice i only used 3 switches in the manual bank switching diagram when i told you to use 6. i used 3 because i didn't think anyone wants to run the menu program since its not going to work anyways =P. also for kid chameleon, you can make that game work if you have a game genie. you will need to enter 2 patches:

address: $000004, data: $0000
address: $000006, data: $04B0

you need a converter to convert these from address and data values, to game genie codes =P. if someone converts these, post them here =D. haven't tested them, but i'm sure they'll 100% work

[paulpsomiadis]

Thanks @oompaloompa!

Also, is there a way I can change my username?

When I created my account I was in a hurry and made a typo in my name (easy to do with a Greek name).

If not - then I'll just ask to get my account REMOVED so I can create a new one...