my batteries are low, just at the start of GPL calc game selling season too, aka math (: Don't wanna flash my calc untill I get some rechargeables. I wish there was flash ram...

what do you mean by flash ram?

D00d, are you serious?!?!? :)
Flash RAM is the memory in TI-83+/SE, 89, and 92+ calcs that makes them so superduper. It allows you to put apps on the calc and store ~100KB (TI-83+), ~1.6MB (TI-83SE) ??(89 and 92+) of stuff on your calc.

Actually, Kerm, you would be talking about Flash ROM. The reason he wants Flash RAM is because (correct me if I'm wrong) it requires less power to operate, and therefore would not need a fresh set of batteries to update the OS. However, the thing about ROM is that the mem stays even if power is removed. Imagine if every time your RAM cleared, you lost your OS. Blah.

You are indeed wrong. There is no such thing as Flash RAM. Calculators use Static RAM (SRAM), which uses a two-transistor latch to store a bit. As long as power is applied, data is retained. This uses more power than Dynamic RAM (DRAM), which is used in desktop computers, but does not have to be refreshed every 100 nanoseconds or so, thereby saving current because refresh circuitry does not have to be powered.

The reason that SRAM is used in calculators is twofold:
-It does not have to be refreshed, so the calculator does not use power as much. (The refresh circuitry needs another clock crystal and a stepper to read and write all the memory addresses before the capacitors in them bleed to nothing.)
-It is usually cheaper, not needing special refresh circuitry.

woops, my bad.

Flash ROM is what I was explaining.
It does not need battery power to upkeep the data, so it is similar to EEPROM.

Not similar, it IS EEPROM (as opposed to, say, UVEPROM).

>As long as power is applied, data is retained.

Flaw with this theory: I removed every battery (even the LCD battery) from my TI-83+, TI-85, and TI-89s and let them sit for a month without power. When I put the batteries back in, the data was still there. Obviously, they don't need power to keep their data.

I kind of noticed that, too. My theory is that there is an extra battery in the microcircuts that cannot be removed (sort of like GameBoy games. They have a lithium battery built in to prevent the user from losing their data). This battery probably only provides enough of a continuous current to "remember" the OS and archived programs. Otherwise, you would have lost your OS.

No, you wouldn't. The OS is held in the EEPROM. The EEPROM will retain its data until it is flashed and overwritten, no matter how long power is removed.
If you remove the batteries from a TI-83 Plus, leave it without power for a short while (so that all the capacitors in the calc discharge naturally) and turn it back on, the RAM is empty - but anything in the EEPROM (or 'Archive') is still there.

Correct. EEPROM, or electrically erasable programmable read-only memory, does not need battery power to keep its data. However, storing data to the EEPROM requires more power than storing to regular RAM or SRAM.

True. It has to erase the area to which it is writing to first, then write the data. EEPROM erases electroniacally, whereas something like UVEPROM will erase the data by exposing the silicon to intense Ultra-Violet light. The worst ROM chips are just PROM - once written to, they cannot be re-used. They are a lot cheaper though - a 12C508A will cost only about £1 or so. (PROM only)

That's kinda dumb... why can't you re-write to it?

The way that PROM chips (can) work is that they have in the memory area many small diodes - a diode representing a binary '1'. When programmed, the programming 'box' will go through and send current the wrong way through the diodes, making them blow (burn out). Now there are areas of memory where current cannot flow (as the diode has gone). These represent binary '0's. Once blown, you cannot actually rebuil the diode. This physical destruction of the diode is where you get terms like to 'burn' or 'blow' a ROM.

Oohh.. yeah, but I thought current could only go one way through a diode (I took a short electronics technology class)

Yes, hence the symbol:
->|-
Current can flow from left-right in that (note the arrow) but not the other way (it is blocked by the line). In the PROM the current flows through the memory in one way only. To change it you force current the wrong way, killing the diode.

That's what I thought (I guess I did learn something from that dang course)

I love how the archive doesn't lose it's memory. That's so cool.

>>even the LCD battery

Do you mean the 3V backup Lithium battery?

Presumably - it is quite close to the LCD.

*shrug* I've always heard of it referred to as the LCD battery, and I'm not one to argue about hardware that I know next to nothing about ^.^

I think I've heard it as the "LCD battery" before, but hey, I know less than you do about it :) I have heard "lithium battery" used more commonly, though (that's normally what I call it).

How about good-ol' backup battery?

I never really thought of it as a backup battery because if you pop one of the AAA batteries, the RAM wipes (if it's on).

that's true...exactly why you should turn it off before changing the batts
lol, did that once or twice myself by mistake :)

Me too, lol. I definitely learned from that mistake :) Now I always turn it off, take out one battery, put in one battery, take out another, put in another, etc. Then turn it back on. Usually that doesn't clear the RAM.

lol...I do that too, even though it is hardwired together so it wouldn't make any difference :)

All you need to do is trun the calc off, take out all batteries, then put in the new ones. Magic.
BTW, Kerm, did you ever make your fantastic mouse driver? I've made a keyboard adapter for my TI based on the one MV made, and if that works I might try a mouse driver.

Yeah, I did make it work. Could you send me a copy of the kbd code? I'd like to take a look.

So, you actually got the mouse to move around the screen, by input of a real mouse? That is pretty nifty, though the screen's too small for it to have any real purpose.

http://calcnews.net/modules.php? name=News&file=article&sid=40

lol...I never even saw this site!

www.radicalsoft.org (MV's site (or one of))
Click 'Hardware'. There's the kbd driver & adapter.
Must have wired 2.5mm stereo jack wrong... won't work (keyboard initialises, but ne keypresses sent).

It seems that I tried exactly the same method about 6months ago - but with lights shining on the screen (it didn't work). It used a couple of logic chips, a 6V set of AAs and 3 transistors. That bit worked, but it wasn't fast enough for any decent results (I got a muddy brown colour!)

I think the key is to have super-bright LEDs, have them on the side, and put a mirror underneath the screen. Plus, the chip's switching speed affects the speed of the color.

no, in fact u are wrong. there is such a thing as Flash Ram. it's not used in calculators, but it does exist. click the link to find out about it. But it is used more as a hard drive then as memory. And also, SRAM is actually quite expensive compared to DRAM. But it is also faster.

Actually, the Flash memory should not be addressed as RAM or ROM. RAM, being Random Access Memory, is erased when the computer is turned off. ROM, being Read-Only Memory, is unalterable. It contains a small, perminent (as in, it is engraved on the chip itself) driver program that launches the OS and loading sequences from the primary storage. Flash Memory, as it should be called, is both ROM and RAM, because it can be changed/altered, but does not go away (even without the back-up battery) when all power is cut. It was designed to be maintained this way because the non-accessible Flash Memory stores the OS.

00ps, my bad. This type of memory is called EEPROM (this from benryves).

Electrically Erasable Programmable Read Only Memory.
Now there's a mouthful.

That's flash ROM, not RAM.

Maybe he means a kind of Flash that requires less battery power to modify?

yes