27 Oct
2011
27 Oct
'11
3:34 p.m.
Chuck Guzis wrote:
Microchip is a very strange outfit when it comes to
the PIC32. Like
the R4000, programming on the PIC32 is present as JTAG. However
Microchip incorporated a rather convoluted version of their SPI
protocol that's translated into JTAG on the chip. I'm sure it sells
a lot of PICKIT programmers, but otherwise, it's been a mystery to me
why this was done. Could it be that JTAG is more or less industry
standard for this sort of thing?
JTAG is a serial protocol that communicates to one or more chips on a JTAG
bus. It is commonly used as the debugging vehicle for some CPU families.
It communicates between a host computer and the debug subsystem within a
target CPU to allow:
1. Run-time debug and breakpoint operations.
2. Boundary-scan that lets you emulate the CPU for the outside circuit.
3. Flash programming since it can be used to generate memory bus cycles.
Vendors often use proprietary serial mechanisms for their pods and JTAG
functionality. I would presume this is to make sure you buy their tools.
Amardeep
27 Oct
27 Oct
3:54 p.m.
On 27 Oct 2011 at 18:34, Amardeep S Chana wrote:
Vendors often use proprietary serial mechanisms for
their pods and
JTAG functionality. I would presume this is to make sure you buy
their tools.
My point was that Microchip on the PIC32 takes their ISP protocol and
covnerts it on the PIC32 chip to eJTAG, which is used by the original
R4000. There are no other programming interfaces, nor is there
anything specifically unique to the ISP interface. The decision of
Microchip to even bother with ISP is a bit of a head-scratcher. I
can program ARM chips just fine with JTAG. Indeed, the PIC32 can be
programmed with JTAG, but Microchip doesn't provide support for JTAG
programming in their toolkit. More PICKIT sales?
--Chuck
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