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Nick

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Joined: 09/06/2011
Location: Australia
Posts: 512

Posted: 11:50pm 27 Dec 2012

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Is there a limit to the number of times one can write to the internal RAM A: drive?

I wish to include some audio MOD files in a program and I am wondering whether it's detrimental to the life of the RAM if the files are loaded and unloaded each time it is run.

Should I load them once and leave them there, checking if they exist next time the main program is run and only loading in their absence?

Nick

hitsware
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Joined: 23/11/2012
Location: United States
Posts: 535

Posted: 12:11am 28 Dec 2012

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There is a supposed limit to all SS memory activity.
(even usb drives supposedly 'wear out')
It's probably best to operate as though this will
happen way sooner than it will (practically)
(to be on the safe side)

graynomad

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Joined: 21/07/2010
Location: Australia
Posts: 122

Posted: 01:37am 28 Dec 2012

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While there may be a theoretical limit to RAM writes I've never heard of anyone considering it in their programming. How many times are some of your variables changed? How often do you think the stack is written to?

Some programs modify RAM locations every mS (or less) for years (or more).

That said

Quote load them once and leave them there

Sounds like better programming practice.
Edited by graynomad 2012-12-29

Rob Gray, AKA the Graynomad, www.robgray.com

MicroBlocks

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Joined: 12/05/2012
Location: Thailand
Posts: 2209

Posted: 02:01am 28 Dec 2012

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Drive "A:" is not located in RAM but in the flash memory.
With a pic32 it is guaranteed to work for at least a 1000 write cycles.

http://ww1.microchip.com/downloads/en/DeviceDoc/61156G.pdf
look at the table on page 191.
"Cell endurance" = 1000
Only the PIC32MX534/564/664/764 device have an extended endurance of 20000.

Above that and you start taking risks.
Reading of course is unlimited.Edited by TZAdvantage 2012-12-29

Microblocks. Build with logic.

graynomad

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Joined: 21/07/2010
Location: Australia
Posts: 122

Posted: 02:04am 28 Dec 2012

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Quote Drive "A:" is not located in RAM but in the flash memory.

Then that's a WHOLE different ball of wax.

Rob Gray, AKA the Graynomad, www.robgray.com

Geoffg

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Joined: 06/06/2011
Location: Australia
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Posted: 12:44pm 28 Dec 2012

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This has been covered before but in essence MMBasic uses wear leveling to extend the flash memories endurance. The practical result varies according to how full drive A: is but typically if you wrote and then deleted a file once a day for every day of the year the endurance would range from 5 to 50 years.

Geoff

Geoff Graham - http://geoffg.net

Nick

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Joined: 09/06/2011
Location: Australia
Posts: 512

Posted: 01:21pm 28 Dec 2012

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I can't seem to be able to get OPTION ERROR working.

I have OPTION ERROR CONTINUE at the start of my code.

Then I test to see if a file exists on A: by trying to access it.

PLAYMOD "A:SOUND.MOD"

If the file doesn't exist under normal circumstances (without OPTION ERROR CONTINUE) the program stops with an error. Do a PRINT MM.ERRNO and I get 6, correct.

With OPTION ERROR CONTINUE, I get a zero for MM.ERRNO.

Am I doing something wrong?

Nick

BobD

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Joined: 07/12/2011
Location: Australia
Posts: 935

Posted: 02:23pm 28 Dec 2012

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That does not seem to agree with the manual. You are seeing the error being suppressed but the manual implies that the error code is still set but MMBasic won't stop for the error and it is up to you to read the error code and deal with it.

Looks like a bug to me.

cosmic frog
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Joined: 09/02/2012
Location: United Kingdom
Posts: 278

Posted: 03:39pm 28 Dec 2012

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Have you had a look at the example in MUSIC.BAS in the colour demos folder?

' First, check if the MOD files are on drive A: and if not. copy them
'
For i = 1 To 3
Option error continue
Open "A:T" + Chr$(48 + i) + ".Mod" For input As #1
If MM.Errno Then
Option error abort
If i = 1 Then
Print "This program will copy three files to drive A:"
Print "The screen will go blank for a while so please be patient"
Input "Press ENTER to continue...", t$
EndIf
Copy "B:T" + Chr$(48 + i) + ".Mod" To "A:"
Else
Option error abort
Close #1
EndIf
Next i

Dave.

MicroBlocks

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Joined: 12/05/2012
Location: Thailand
Posts: 2209

Posted: 09:24pm 28 Dec 2012

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@Nick,

Could it be that you check the MM.Errno a little to late.
I can imagine that other statements could reset the value.
I guess the only one who really knows is Geoff. :)
In samples the test for MM.Errno is immediately after the line that could throw that error.

However, the best way is to get the information you want without the need to check errors.
You can use DIR$ to check for a files existence.

Edited by TZAdvantage 2012-12-30

Microblocks. Build with logic.

Geoffg

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Joined: 06/06/2011
Location: Australia
Posts: 3165

Posted: 12:28pm 29 Dec 2012

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Thanks folks, you have found a bug in the PLAYMOD command and I will fix it in V4.2.

Other commands should set MM.ERRNO correctly so you could use this as a workaround.

OPTION ERROR CONTINUE
OPEN "A:SOUND.MOD" FOR INPUT AS #1
IF MM.ERRNO THEN GOTO <error handler>
CLOSE #1
PLAYMOD "A:SOUND.MOD"
<continue with the program>

BTW the only commands that should change MM.ERRNO are file related commands. So, for example, PRINT MM.ERRNO would not change the value of MM.ERRNO.

Geoff

Geoff Graham - http://geoffg.net

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