Compact Flash (was Re: Vector Table)

[Chris Johns]

mrada wrote:
> 
> Unless I am not realizing what you are saying here :-), but isn't DOSFS
> treating the CF as a file system?

It does as CF has an IDE controller built in that is either IO or memory 
mapped. I do not think you can map the full address space of a CF into a 
processor's address space. You need to seek the block of the CF memory 
you want and read it.

If you look at media type cards or memory devices you will find they 
have an SPI type interface. Again you cannot map to a processor's 
address space.

> I was think of making the CF addressable
> in memory.  Like EEPROM is.  Maybe you can give me a little more information
> or examples of how you used your CF.

You can treat the CF memory as an indirect block of memory rather than a 
file system. I am sure niche apps exist where this is a valid approach.

We have a boot rom that can mount a disk (partition table and various 
FAT formats), read a boot script and/or load an RTEMS executable image 
into memory where is runs. We use 32bit wide DRAM and small boot flash 
devices in these apps. RTEMS can then mount the same disk, write new 
images, handle files etc. The DOS format allows me to mount the CF in a 
cheap USB type reader and load new RTEMS images. The downside is you 
need to maintain a valid file system. A loss of power at the wrong time 
can require a disk check.

-- 
  Chris Johns, cjohns at cybertec . com . au