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#21
Re: flashcart for sale??
Posted on: 2006/6/21 12:20
Administrator
Joined 2000/1/8
Germany
2519 Posts
Highscore Top10Highscore Top ScoreCoder#1 PosterHOTY09 1stLong Time User (15 Years) App Coder90+ Game Ratings
really great work on the pcb, pat. gotta love that little vb in the bottom left corner. <3
:D
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#22
Re: flashcart for sale??
Posted on: 2006/6/21 13:13
VUE(xpert)
Joined 2003/7/27
Australia
267 Posts
CoderLong Time User (15 Years) DonatorApp Coder
If you have the space to waste on a cute picture of a VB you have room to install 2MB of ROMs


Does this use capacitors or any other (non-flash) components? It looks like you soldered something to the board, but I can't see what.
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#23
Re: flashcart for sale??
Posted on: 2006/6/21 16:08
Nintendoid!
Joined 2004/10/25
USA
100 Posts
CoderLong Time User (15 Years) App Coder
Basicaly for the boot loader you have to take over the top block of flash ram and virtualize the interupt table. So make a 8k program that loads a list of avalible games from the top of saved ram space, and gives you a menu of games to play or the option to load a game from the link port. thain when a game is running and it throws an interupt your interupt handler just jumps to the relocated game interupt table located either at a blank area in rom or at the end of sram space.

Your cart could have a 32k sram chip (or larger) to add extra space for the jump tables and other values. Besides you want to sell the cart as a development device and not a space invaders loader. So having the uper 8k of rom being inacesible would not be a big deal.

Also when reflashing the cart you lock the uper 8k in a 'boot block' (so get a top boot block chip) that can not be overwriten without some extra gyrations. 8k would be enough for your loader, a flash routine, the GDB (GCC Debuger) loader/debug routines and a generic set of librarys.

Speking of GDB, gdb has a rom resident boot loader that is designed to run over the serial port. This is the best way to implement the serial port loader since it already does everything you would want to do (read/write in bytes/blocks to any address space) plus it would let you run a debugging session right in hardware, great for development.

DogP, your flash cart is beautiful! Please give me the schematics and I will add an sram and /WE controll logic for you. I have $50 in free PCB development coming to me and I want to use it up.

David
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#24
Re: flashcart for sale??
Posted on: 2006/6/21 17:52
PVB Elite
Joined 2003/7/25
USA
1507 Posts
PVBCC 1stCoderContributor#3 PosterHOTY09 EntryLong Time User (15 Years) App CoderPVBCC 2010 EntryPVBCC 2013 Entry
Thanks for the compliments guys... I spent some time over Christmas break designing it, but then started the next semester of school and never got around to ordering it. Finally after last semester I got around to sending in the order. I basically got the most stripped down model (no soldermask, no silkscreen, no depanelizing, etc) since I didn't want to spend extra on something that might become a (really bad) paperweight.

Lameboy... actually... I can do 2MB of ROMs... EPROM only though :/ . A PLCC 27C080 will fit right in... I just need to change the A18 and A19. I've only found PLCC OTPs though, which is even less useful (unless I want to pirate Golf or something ;) ).

The cart has 3 capacitors... the ones in the corners are .022uF, the one in the middle is 4.7uF. That H looking thing is actually for an inverter to use A22 as an inverted /WE... but I was playing with it on the logic analyzer last night and I think I've got a better way :) . I wanted to use /ES, but you need /CE and /WE low with /OE high to program... expansion disables both CE and OE :/.

I'll let you know tonight if my other idea works... it looked good at 4AM, but I needed to get up this morning for work, so I decided to put it off until tonight ;) .

David... I'd be glad to send you the design, but I did it with DipTrace, so you need the full version to be able to export to get the design made (30 day full trial is fine). I liked the interface, so I started making the design, then at the end realized that it's totally useless without the full version :( .

Personally... I wouldn't make another PLCC style flash cart though... if the in-cart programming works, I'd go with a single 16+mbit 16 bit wide chip. That would give a lot more room for the SRAM chips, and get rid of the messy sharing of the address/control lines (well... it'd just share with the SRAM instead :P)

DogP
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#25
Re: flashcart for sale??
Posted on: 2006/6/22 1:33
VUE(xpert)
Joined 2003/7/27
Australia
267 Posts
CoderLong Time User (15 Years) DonatorApp Coder
This is the the EEPROM I was thinking of using. The 28C64 claims it can be read and written to like SRAM, but as it is EEPROM no need for a backup battery.

And as for the /ES problem, couldn't you tie both /WE and /CE to it? And when you say /OE is disabled do you mean its high or low, because IIRC writing needs it high/disabled. You could also use CS2 because IIRC CS2 is only high when SRAM is accessed.
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#26
Re: flashcart for sale??
Posted on: 2006/6/22 2:57
PVB Elite
Joined 2003/7/25
USA
1507 Posts
PVBCC 1stCoderContributor#3 PosterHOTY09 EntryLong Time User (15 Years) App CoderPVBCC 2010 EntryPVBCC 2013 Entry
Well if you tied /WE and /CE together, then you couldn't _read_ from the flash, since any accesses to the ROM wouldn't be to the expansion area, which would mean CE is disabled. And when I say OE (and CE) is disabled I mean high, like the enable is disabled. But like I said... I think I got it taken care of... going to mess with it now.

DogP
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#27
Re: flashcart for sale??
Posted on: 2006/6/22 5:29
PVB Elite
Joined 2003/7/25
USA
1507 Posts
PVBCC 1stCoderContributor#3 PosterHOTY09 EntryLong Time User (15 Years) App CoderPVBCC 2010 EntryPVBCC 2013 Entry
WOOOOOOOOOOOOOOOOOOT! It worked! Anyone remember that pesky pin 5??? Well... that's a /WE! (not to be confused with a /Wii ;) )

Anyway, gonna modify the couple carts and make sure it never screws up, but watching it on the LA it doesn't look like it'll be a problem. Then I'll work on a nice flash writing program from the link port. It shouldn't be too tough... I've still got my link port dumper program, adding write capability shouldn't be tough :) .

DogP
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#28
Re: flashcart for sale??
Posted on: 2006/6/22 14:19
VUE(xpert)
Joined 2003/7/27
Australia
267 Posts
CoderLong Time User (15 Years) DonatorApp Coder
...It took you this long to test writing? I'd have thought you would have tested that way back when you found the extra address lines years ago. :woah:

Way to ruin the fun of rerouting all the CSs/Es in order to read/write flash and RAM.


Still, its great to know no juggling will be involved in writing flash. Just hope it works.


...And about a 2MB ROM, what type chip were you going to use? PLCC only goes up to 512Kx8.

...And while were on that, if I were to use 4x512K chips, how would I make sure the higher ones are only active above 1MB and vice versa?
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#29
Re: flashcart for sale??
Posted on: 2006/6/22 16:13
PVB Elite
Joined 2003/7/25
USA
1507 Posts
PVBCC 1stCoderContributor#3 PosterHOTY09 EntryLong Time User (15 Years) App CoderPVBCC 2010 EntryPVBCC 2013 Entry
Actually, I had tested writing in the past, but I never saw any action on that line as suspicious because it's pretty short, and lookes random (it's also connected to /UWR on the PSRAM, which I had seen before, but I didn't understand why they brought it out to the cart edge).

If I just watch the line it doesn't particularly look like it's doing anything, but when I set the trigger for /CE, I noticed there were two pulses at the same time as my write (wrote 32 bits, which is two 16 bit wide cart writes), and on a read I noticed the two pulses moved back after CE was disabled, which is probably writing the data it just read.

Anyway, yeah... it works, I tied /WE to pin 5, played a couple different games, let it run for about an hour, no problems. Then I tested the write sequence and was able to write with no problems, then did a chip erase and ate my own program :) . I gotta get the app into memory so I can do this stuff freely... hopefully I'll get some time to mess with it today.

For the 2MB ROM, there are PLCC 27C080's (EPROMs)... same as the 27c080/27c801 DIP that come in 8mbit, except these are the PLCC package. Same pinout except A18 and A19. I wouldn't even think about trying 4 PLCC chips... see how much of a mess it is tying all of those pins together on the 2 PLCCs? It'd be a nightmare with 4! It's not like DIP where you have the spacing between the pins that you can run all of the common lines straight on a line, and since there's pins on all 4 sides you can't just route them there either :/ .

DogP
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#30
Re: flashcart for sale??
Posted on: 2006/6/22 17:32
VUE(xpert)
Joined 2003/7/27
Australia
267 Posts
CoderLong Time User (15 Years) DonatorApp Coder
I know there'd be a lot of tracks, but I was planning on making a cart that takes up the entire area inside the cart, not just the size of the curent VB PCBs.
Hope that would leave enough space for routing.


...So, any plans for a flashcart + SRAM/EEPROM?
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