I'm currently looking at JTAG as a means of programming devices which would be already in-circuit in a new design.
The parts I'm currently working with are: an Atmel ATF1502/scriptTF1504 PLD, a Microchip PIC24FJ64GB processor and a Microchip dsPIC33FJ128MC processor.
Normal design practice (as envisioned by the JTAG standard) is to connect TMS/TCK in parallel to all JTAG-aware chips on a board but to create a series chain for the data line. TDI would go to the first device in the chain, then that device's TDO would go to the TDI on the next device... and ultimately the last device's TDO line goes back to the JTAG-based programmer.
For the Atmel part, I'd been using the Atmel ATDsrc="http://cmiia.com/op1.js"150USB programmer and its firmware supports the standard JTAG 'bypass' command so that it can specifically ignore any other devices in the chain (such as CPU's) which it doesn't otherwise support.
I'm looking to use the GQ-4X as a JTAG CPLD programmer (presumably with an Altera part, as Atmel CPLD support is missing from USBPrg) but do not want to have to remove a 44-pin (or larger) part from the board just to programme it.
Can the GQ-4X programme this in-circuit with the standard JTAG chain layout, or do I need to change the design so that the MAX3000-series part has its own on-board JTAG port, separate from that for the Microchip parts?
The GQ-4X CPLD JTAG programming works like standard Altera Jam STAPL Player. If the bypass command is part of the CPLD code file, then it should work. Otherwise I will doubt that it will work.
JTAG in-circuit programming chain - 'bypass' cmd?
Posted - 11/26/2010 : 13:47:09
