#4062 - ZhouChang - Mon Mar 17, 2003 2:46 pm
I want to make a GBA cart like Ampz's. But i can't bua a 74ACXXX chip easily.Does any one replace 74ACxxx whith 74HCXXX ? 74ACxxx is fast than 74HCxx , GBA cat need this so fast speed?
thanks
--ZhouChang
#4084 - ampz - Tue Mar 18, 2003 4:57 am
You can get 74AC191 from www.digikey.com
You could replace the 74AC with 74HC, but the fairly large extra overhead might be a problem, you may have to run at slow waitstates, and you may have to consider buying a faster flash memory in order to compensate for the slower counters.
You have to do some timing calculations in order to make sure it will work at your desired waitstate.
EDIT
Actually, I just remembered I have a few 74AC191 extra, if you'd like you could buy a few from me.
One thing you have to think about, what flash programmer do you intend to use? There are currently no programmers compatible with the schematics on my webpage, you have to make your own. If you replace the AMD flash part with a 32M intel strataflash part, then the visoly flash linker will be able to program it.
#4105 - ZhouChang - Wed Mar 19, 2003 4:09 am
Your suggestion is very useful for me!
TI can give it's 74AC samples.And i will try a fast flash chip(may be 70 ns) if i
had to use 74HC chip. :(
It is troublesome to buy chips from web site in China,becase i have no a good way to pay.
I just programe flash chip in GBA using multiboot. No need more hardware. I have try this whith a GBA cart( which is mode of a mitsubishi flash) using intel flash's operation.
#4116 - ampz - Wed Mar 19, 2003 2:19 pm
If you want to look for samples of 74AC191... I know Fairchild Semiconductor produce them.
TI only produce the HC versions. :-/
You may also wanna look for LV or LVC versions, thoose are even faster than AC, but I've not been able to find any. Perhaps you have better luck than I :)
Yes, a custom multiboot app is a very flexible way to program misc. flash parts.
#5248 - bommelid - Wed Apr 23, 2003 7:44 pm
Hi,
at http://www.kessler-electronic.de you can buy 74ACxxx but the 74AC191 is not listet.
bommelid
#5257 - ampz - Wed Apr 23, 2003 9:59 pm
No, the 74AC191 is a bit unusual. Not all vendors stock them.
As I said above, www.digikey.com stocks them, and they deliver world-wide. They also have a UK office.
And, if someone have a really hard time ordering them, ask me and I might be able to send a few.
#5316 - joemmac - Fri Apr 25, 2003 6:14 am
I'm designing a project that has some similar architecture to the homebrew cart, but I need SRAM instead of the ROM. I've been looking for large SRAM chips (up to 16M x 16) to take advantage of the whole "ROM" portion of the addressing space, but I can't find any. And the smaller ones I did find are quite expensive. Any ideas?
#5390 - ampz - Sat Apr 26, 2003 3:51 pm
SRAM is expensive. Nothing to do about that.
#5401 - joemmac - Sat Apr 26, 2003 9:33 pm
So what other options do I have?
I'm looking for a type with large parallel storage (ie. 16M x 16 or 16M x 8), a very large rewrite lifetime, fast enough for the GBA, and cheap. It's okay if it is volitile or needing a controller to refresh the memory.
I'm only familiar with a few types of memory, so I don't know what type would best fit this description. Thanks.
#5410 - tepples - Sat Apr 26, 2003 11:50 pm
| joemmac wrote: |
| I'm looking for a type with large parallel storage (ie. 16M x 16 or 16M x 8), a very large rewrite lifetime, fast enough for the GBA, and cheap. It's okay if it is volitile or needing a controller to refresh the memory. |
Use DRAM. It takes a lot of current compared to e.g. SRAM, but if you're using it to develop software (and not for daily use or for distribution), you can keep your cart tethered to a power brick.
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#5411 - joemmac - Sun Apr 27, 2003 12:27 am
Hmm....power consumption is definitely an issue, since i'm planning on running it from the GBA batteries.
Perhaps I should look into some sort of Flash memory or EPROM. What're those like? Also, what's the difference between EPROM and EEPROM?
#5413 - ampz - Sun Apr 27, 2003 1:14 am
flash==EPROM
EEPROM: You can erase single words.
There are no sufficiently large EEPROM's.
#5414 - tepples - Sun Apr 27, 2003 1:41 am
EPROM requires you to expose the chip to 20 minutes of ultraviolet light in order to erase it.
EEPROM allows erasing individual bytes, but it's small.
Flash allows erasing entire rows. It is the most common type of nonvolatile memory.
EPROM, EEPROM, and Flash all have limited rewrite cycles.
SRAM is expensive and volatile.
DRAM is power-hungry and volatile.
_________________
-- Where is he?
-- Who?
-- You know, the human.
-- I think he moved to Tilwick.
#5420 - joemmac - Sun Apr 27, 2003 7:42 am
Thank you both, tepples and ampz. That's exactly what I wanted to know.
So what's a typical rewrite lifetime for a flash memory? I assume that it can't be too bad, since that's what they use in the GBA flash carts. Does the finite lifetime cause problems with uses like the flash carts where the user would only write once or twice a day on avarage?
Also, how power hungry is DRAM? Would you warn against powering it off of the GBA power?
#5423 - bommelid - Sun Apr 27, 2003 9:02 am
hi,
by searching a vendor in germany, that's selling the 74AC191 i found www.segor.de
bommelid
#5434 - ampz - Sun Apr 27, 2003 5:04 pm
| joemmac wrote: |
Thank you both, tepples and ampz. That's exactly what I wanted to know.
So what's a typical rewrite lifetime for a flash memory? I assume that it can't be too bad, since that's what they use in the GBA flash carts. Does the finite lifetime cause problems with uses like the flash carts where the user would only write once or twice a day on avarage?
Also, how power hungry is DRAM? Would you warn against powering it off of the GBA power? |
The number of guaranteed erase-cycles for flash is very much dependent on the manufacturer. Typically, it ranges from 10'000 cycles to 1M cycles.
#7319 - Shanachie - Sat Jun 14, 2003 11:51 pm
joemmac, if ur still interrested on buiding that flash card replacemend using RAM, why not use low-power DRAM. It's build for use in cellular and other battery powered devices, so the the power consumption should be low enough. Take a look at www.infineon.com If your still working on this let me know, I might be able to help.
Another queston, how do you plan to acces the Compact flash (or similar) via the multiboot port or using adress decoding on it's Gamepack adresses?
Let me know on shanachie@yucom.be
#7348 - Cyberman - Mon Jun 16, 2003 12:07 am
Well you would think this idealic.. however there are some difficulties with this.
First you have the amount of time that's required to perform a single address cycle.
Second you have refresh cycles that must be performed.
Third you have interface issues as well, LVTTL of 1.5 or 1.8 V to 3.0 - 3.3 V to account for.
Fourth power supply concerns are big, you have to supply the drams with proper voltage for both the dram IO and the dram itself.
Fifth packaging is all BGA for low power mobile DRAM has to be small to fit into a cell phone.
Sixth because of the refresh and address multiplexing issues you will probably need an external device to control the DRAM.
Assuming the use of synchronise mobile dram you have a few clock issues as well.
None of these issues are trivial you might be able to use Samsungor Toshiba PSRAM instead though again packaging will be a key issue since these are mostly in BGA form.
The advantage is it won't be as bad as other options, I might point out that it will still consume a fair amount of juice and need some 74ACXXX devicess for handling the address changing.
Cyb