JTAG how to

debugging

JTAG (Joint Test Advisory Group) is a serial interface intended for integrated circuit testing. It is specified in the JTAG/IEEE 1149.1 standard.

Basically it consists of a serial data in signal, a serial data out signal, a clock signal and a serial control signal. The control signal runs a state machine of 16 states controlling the interpretation of the serial data signals.

The standard specifies test control logic cells situated between the chip internals and I/O pins, so that the pin states can be monitored and controlled.

The actual debug interface is dependent of the particular processor chip the JTAG unit is attached to. For example, the ARM7TDMI has JTAG scan cells between the ARM core and the rest of the chip. there is also a hardware debug unit controllable via the JTAG scan chains.

HTH

Tauno Voipio tauno voipio @ iki fi

So is it possible to use GDB do debug a target such as the ARM that supports debugging via JTAG? Are there any eeproms that support programming via JTAG? Does anybody know of any docs on how to set up JTAG on linux using one of the many JTAG paripherals for PCs? I have some experience with Motorola's BDM debugging system. I was able to set up GDB and debug my coldfire board through a parallel port BDM interface. What would be the most suitable JTAG set up for a hobbyist looking to debug a uC board they built that supports JTAG?

Dave

Tauno Voipio wrote:

Thats an interesting question about GDB, would be interested to find out about that.

umm theres info at :-

Thats pretty much where Ive got my information from so far,

My interest came with the jtag because I got given a router that has an arm

9 connexant IC and also a 14 way jtag port, so I was interested in porting uClinux to it.

greg

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