Reading DEVID, DEVREV and fuses on PIC24

[Oli]

Hi all,

I'm trying to read the following address' on the PIC24FJ256GB110

DEVID (0xFF0000)
DEVREV (0xFF0002)
CW1 (0x2ABFA)
CW2 (0x2ABFC)
CW3 (0x2ABFC)

This document: http://ww1.microchip.com/downloads/en/DeviceDoc/39907a.pdf

indicates the address' I have put in brackets.

I have attempted to access these like this:

[Ttelmah]

#word, locates a 16bit variable into the _RAM_ at the specified location.
Which doesn't exist.

You want to access the _ROM_.

Key thing to understand, is that unlike the PC, the PIC, has completely separate RAM, and ROM memory spaces. This makes it simpler to get good performance without having to fiddle around with cache, since the chip can be initiating a ROM read/write, at the same time as it is also reading/writing the RAM. Downside, is two complete address buses, and control lines for these, and that the user needs to be aware of what memory 'space' they want to talk to.
Accessing the ROM, is more complex than a simple read, with you having to setup an address pointer, and trigger a flash read cycle, to transfer the value into RAM where you can then inspect it.

Look at the 'read_configuration_memory' instruction, and the 'read_program_memory' instruction.

Best Wishes

[Oli]

Thanks Ttelmah - really should have though of that! All resolved now.