[fpc-devel] Is target mips-embedded possible / planned?

Michel Catudal mcatudal at comcast.net
Wed May 22 22:31:10 CEST 2013

Le 2013-05-22 03:20, Michael Schnell a écrit :
> If you install some software on the target for self-programming, you of course can use any (serial) interface to transfer the user software and burn it into the Chip's Flash. That way an USB-to-serial Adapter providing async, SPI and/or I²C offers
> perfect speed. (As the serial USB Adapter you can use the PICKit hardware which is rather cheap and comes from Microchip pre-programmed with the appropriate firmware as "Serial Dongle" or similar.
> Of course you can't (easily) do debugging via such a serial interface. here using the debug hardware built in the chip seems much more appropriate.
> The debugging (and "hardware" Flash programming) pins of the PIC chips are not necessary handled in a "bit-banging via USB" mode. The ICD-3 Adapter (but supposedly not the PICKit) uses internal intelligence here and the image to be programmed is
> transferred in blocks of bytes via USB.
> -Michael
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I am talking about the connection to the processor. If you use JTAG this would be faster because you have more pins to bit bang with.
With the Microchip specific hardware they use less pins so you have to do some multiplexing. If you have to wait for data to be done then the time saving with faster bit banging wouldn't help you.

With the PE you download that into the processor and then you just fill a buffer and tell the PE to copy into flash. Without the PE you need to program a word at a time. There is no way that you can compete in speed with Microchip's PICKit or ICD without
this. I saw the source for the PICKit and it uploads the PE for reflashing. As for the emulator it is likely to use either the JTAG or Microchip's own hardware. The USB port is on the emulator and not the processor being debugged. There is some
intelligence as in the Atmel and NEC debuggers for debugging but not for programming. For programming the PE is used. Since Microchip will not release information on their proprietary debugging we need to use  debugger that support MIPS debug mode.
I don't recall seeing debugging in the source code released for the PICKit. Correct me if I am wrong.


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