Post by thread:[EE]: Is it possible to write protect a Flash Card

There's a project called Linux Router Project (lrp.c0wz.com) that is a stripped down version of linux that runs off a single floppy and can turn an old 486 PC into a firewall/router. In the past several months there has been discussion on their mailing list about alternative boot media. The most ideal is a compact flash card. There are several 'adapters' that allow a flash card to connect to the IDE interface of the machine. The problem is with security. With a floppy disk, you can physically write protect with the tab. So there's my question: Is it possible to 'physically' write protect a flash disk? In this particular setup, the flash disk is only used for booting. Everyting is run from a RAM drive, so the flash card is only needed during booting, so it could disappear (as far os the OS is concerned) until a reboot. Any thoughts or info? Thanks, Chris -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Firstly, I believe there is a write protect built into the IDE specification, which the compactflash follows. Failing that, in order to write to the compact flash one must set the registers up for a write operation. Using a pld or other logic one could prevent specific types of writes to those registers (allowing other register access for reads from the media). There may be a little more to do to indicate that the write has failed (so the OS doesn't go crazy), but I'm certian it could be done. -Adam Chris Carbaugh wrote: {Quote hidden}> > There's a project called Linux Router Project (lrp.c0wz.com) that is a > stripped down version of linux that runs off a single floppy and can > turn an old 486 PC into a firewall/router. > > In the past several months there has been discussion on their mailing > list about alternative boot media. The most ideal is a compact flash > card. There are several 'adapters' that allow a flash card to connect > to the IDE interface of the machine. > > The problem is with security. With a floppy disk, you can physically > write protect with the tab. So there's my question: > > Is it possible to 'physically' write protect a flash disk? > > In this particular setup, the flash disk is only used for booting. > Everyting is run from a RAM drive, so the flash card is only needed > during booting, so it could disappear (as far os the OS is concerned) > until a reboot. > > Any thoughts or info? > > Thanks, > > Chris > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

>Any thoughts or info? Why not just remove the flash card once the machine has booted? OK you may want to have it automatically reboot after a power down which may not make this possible. How about having Linux mark all the files RO? -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> In the past several months there has been discussion on their mailing > list about alternative boot media. The most ideal is a compact flash > card. There are several 'adapters' that allow a flash card to connect > to the IDE interface of the machine. Have you looked at using SmartMedia and a 1.44 floppy adaptor? The adaptor at least is relatively inexpensive. Peter -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

On Tue, 10 Oct 2000 15:55:29 +0100, you wrote: >> In the past several months there has been discussion on their mailing >> list about alternative boot media. The most ideal is a compact flash >> card. There are several 'adapters' that allow a flash card to connect >> to the IDE interface of the machine. > >Have you looked at using SmartMedia and a 1.44 floppy adaptor? The adaptor >at least is relatively inexpensive. > >Peter I've not used one, but I'd be extremely surprised if it actually emulated the floppy format to the extent that you could boot from it - I suspect it comes with a driver to talk to the interface via the floppy head using its own protocol, with the head held in a fixed position. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

I've used Intel FLASH cards that had itty bitty little write protect switches on the edge of the card. Cisco uses 'em. On Tue, 10 Oct 2000, Chris Carbaugh wrote: {Quote hidden}> There's a project called Linux Router Project (lrp.c0wz.com) that is a > stripped down version of linux that runs off a single floppy and can > turn an old 486 PC into a firewall/router. > > In the past several months there has been discussion on their mailing > list about alternative boot media. The most ideal is a compact flash > card. There are several 'adapters' that allow a flash card to connect > to the IDE interface of the machine. > > The problem is with security. With a floppy disk, you can physically > write protect with the tab. So there's my question: > > Is it possible to 'physically' write protect a flash disk? > > In this particular setup, the flash disk is only used for booting. > Everyting is run from a RAM drive, so the flash card is only needed > during booting, so it could disappear (as far os the OS is concerned) > until a reboot. > > Any thoughts or info? > > Thanks, > > Chris > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > > > --- The most exciting phrase to hear in science, the one that heralds new discoveries, is not "Eureka!" (I found it!) but "That's funny ..." -- Isaac Asimov -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Chris Carbaugh <spam_OUTcjtech2000TakeThisOuTyahoo.com> wrote: > The most ideal is a compact flash card. There are several > 'adapters' that allow a flash card to connect to the IDE interface > of the machine. > > The problem is with security. With a floppy disk, you can > physically write protect with the tab. So there's my question: > > Is it possible to 'physically' write protect a flash disk? Chris: From the CompactFlash spec, section 4.4.6: Wprot: this bit is always zero (0) since the CompactFlash Storage Card or CF+ Card does not have a Write Protect switch. So the answer's no; you can't electrically write-protect a CF card. -Andy === Andrew Warren --- .....aiwKILLspam@spam@cypress.com === Cypress Semiconductor Corporation === Interface Products Division, S.D. === === The opinions expressed above do === not necessarily represent those of === Cypress Semiconductor Corporation. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> >Have you looked at using SmartMedia and a 1.44 floppy > adaptor? The adaptor > >at least is relatively inexpensive. > I've not used one, but I'd be extremely surprised if it actually > emulated the floppy format to the extent that you could boot from it - > I suspect it comes with a driver to talk to the interface via the > floppy head using its own protocol, with the head held in a fixed > position. Confession - neither have I. But a friend of mine who has been extolling their virtues was waxing lyrical about the ability to put them into any machine going (WinX, Linux etc.) - with no mention of drivers. Peter -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

>ideas You can power down the flashcard after it has been read. The interface usually allows hotplugging (PCMCIA). One can physically hack this using a flipflop (RS) that is set after booting by the program (actually by a simple utility that you write) and disables the IDE chip select signals (perhaps through a parallel port pin). The flipflop can only be reset at boot time (cold reboot) by the hardware. Incidentally this also works with normal IDE drives. Force spindown and then flip the interface bit. Some IDE drives have a write protect jumper (not advertised). Better, use a bootable CDROM instead of the IDE drive with a burned system CDROM in it. It can be an older 4x standard ATAPI drive with a BIOS set accordingly ;-). Much better than CF price-wise is a flash card (only ISA available afaik). These can be populated with just enough flash to hold you r system and have INT13h interface so LILO and (b)zImage will use them fine. A CF card is overkill since 2M of flash hold more than a single floppy, and that's a single chip that costs less than 1/10 of the price of a CF. The etherboot/netboot package constains a flash BIOS extension interface schematic fyi. Also, a network card has a ROM socket where BIOS extensions can be added to implement almost anything. The elegant solution is a PEEL (?) with a program that disables the write sector(s) and format commands. This I have been involved with when PEELs were many gates ;-). Our solution caused a system reset upon write attempt by decoding the sector write and format commands using LSI logic. Hehe. good luck, Peter -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Bond Peter S-petbond1 <PICLISTKILLspamMITVMA.MIT.EDU> wrote: > > > Have you looked at using SmartMedia and a 1.44 floppy adaptor? > > > The adaptor at least is relatively inexpensive. > > > > I've not used one, but I'd be extremely surprised if it actually > > emulated the floppy format to the extent that you could boot > > from it - I suspect it comes with a driver to talk to the > > interface via the floppy head using its own protocol, with the > > head held in a fixed position. > > Confession - neither have I. But a friend of mine who has been > extolling their virtues was waxing lyrical about the ability to > put them into any machine going (WinX, Linux etc.) - with no > mention of drivers. Peter: The FlashPath floppy-drive adapters for SmartMedia cards DO require drivers... And besides, the SmartMedia write-protect sticker is only a "suggestion" to the host; it doesn't electrically disable writes as many floppy-drive write-protect switches do. -Andy === Andrew Warren --- .....aiwKILLspam.....cypress.com === Cypress Semiconductor Corporation === Interface Products Division, S.D. === === The opinions expressed above do === not necessarily represent those of === Cypress Semiconductor Corporation. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.