Re: JTAG and flash

Alice wrote: 
I'm new to learning about jtag and it's capabilities, and my professor
isn't helping me at all.  I understand jtag is mainly used in
processors, but I was reading on Altera's website about a flash chip
(EPM3032A) they use that has jtag support.  What jtag device would I
need to communicate with a flash chip like that?  I understand there
are jtag devices that support many versions of arm, mips, xscale, etc.
but I don't know which would be appropriate for flash memory.  I
appreciate any help.


JTAG (Joint Test Advisory Group) is a simple serial bit
interface. It specifies a chip-testing access connection
located on an IC between the external pins and the chip
internals.

A JTAG device is just a bit-bang connection with four bits
(TRST, TMS, TCK, TDI) to the device under test and one bit
(TDO) from the device.

The devil lies in the sequencing of the bits,
often wholly handled in software.

The interface is described in the IEEE 1149 standard,
which is sold by IEEE (http://www.ieee.org/) and thus
not available for free in the Net.

The JTAG programming interfaces on programmable chips
are manufacturer and chip-specific. The data source
for these are the data sheets of the chips.

HTH

--

Tauno Voipio
tauno voipio (at) iki fi


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