Lpc2000

ovidearistide wrote:

>Hi,
>
>I am trying to program my flash memory via the JTAG interface.
>However, I am unable to find enough documentation on the JTAG interface.
>Can anyone give me a kickstart?
>
>I am trying to flash in two ways:
>1) From the flash itself (Firmware update).
>2) Externally (initial flash).
>
>Ad 1)
>This is the most important one for me.
>To achieve this I need to execute my firmware update code in RAM (and 
>make sure that interrupt vectors and such reside there as well).
>I believe I have to use IAP. JTAG is also a serial interface, but I 
>don't think it is possible to connect ISP and JTAG (UART only). IAP is 
>not really a problem, but I do not know how to connect my IAP 
>implementation to the JTAG interface. So basically: How do I copy data 
>over the JTAG interface to RAM?
>  
>
In itsy-bitsy steps.  JTAG is merely a series of very long shift 
register chains.  These shift registers allow access to the 
micro-internals of the CPU.

Historically, JTAG was devised to meet two needs:

1. Auto Test Engineering (ATE) was faced with higher and higher density 
boards that they needed to test.  The old "bed of nails" vacuum fixtures 
were no longer able to work on these board.

2. Software / Hardware engineers found it difficult to use clumsy pods 
to either clamp onto or replace the new surface mounted CPU chips.

So, JTAG was born.

There is a lot of information regarding JTAG on the net, it is an IEEE 
standard.  You can purchase the document, or, find various tutorials + 
docs for free on the net, or, you can take apart / work with JTAG 
software as found on sourceforge and other sites offering OSS.


>Ad 2)
>I can use the Philips ISP flash tool to flash via the UART interface or 
>any commercially available tool via the JTAG interface. But I want to 
>be able to batch this process (and maybe configure it). I must use the 
>JTAG interface and I am the only budget available. :-)
>
>  
>
Well, you can save money, but you will spend time, lots of it, writing a 
TAP controller to run the JTAG.

Regards,

TomW


-- 
Tom Walsh - WN3L - Embedded Systems Consultant
http://openhardware.net, http://cyberiansoftware.com
"Windows? No thanks, I have work to do..."
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