JTAG multiple devices

Not a chance.... Each vendor will have their own software implementation as well as their own hardware interface. The only commonality will be the names of the signals at the JTAG end....

Because many silicon vendors keep JTAG accessible hardware on their chips which goes beyond boundary scan secret; then, they give the data some "firm" which is allowed to collect a few thousands per sold cable - or do it themselves. The cash they collect on that is negligible, but once you give in they have you under control. An astonishingly low number of people seem to object paying ransoms like that. If you can do all you need via boundary scan only, though, there should be some cheap way to do it - open source or whatever. (I cannot name any because the tols I use have been written here and run under DPS which you don't have).

Dimiter

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Yes, we object. Especially when we need a few hundred production testers and programmers. We don't need stinking Window Point and Click either (make no sense in production environments), just connect and power it up. We spent hundreds of hours on development (to save hundreds of hours in production), but it would still be cheaper overall. We make the custom device for less than $10 each.

Following Atmel specs, we could SPI program the AVR and JTAG boundary scan them. We are unable to do JTAG programming as stated in the AVR specs. So, we end up with both interfaces on every production board.

Hmm, I did hope you would come in with this sort of a message :-).

I know I am not alone in that - but I think my "astonishingly low" still applies...

Dimiter

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Ok, so if you have different components on your board sharing the same JTAG connector, you have to have different JTAG devices as well? And you connect which ever JTAG device that corresponds to the chip you are testing? Is this how it goes?

Yes, we poll the Jtag/Isp IDs and decide how to test/program the board automatically.

I have had no problem programming Atmel devices using the JTAG interface. I use an altera byteblaster and my own software. AFAIK there is some sort of issue if the AVR is not the only device on the chain, but IIRC it stops one accessing the other devices, and not the AVR itself.

Regards Anton Erasmus

Good to know that it could work. I might get back to it later. For now, ISP works fine for us. However, it would simplify our interfaces if we can do everything in JTAG.