nRF24LU1+: read flash using MOVX or MOVC

[NGO]

Hi,

We tripped on an odd bug: we were getting corrupted data from flash if Keil's C51 compiler used a MOVX instruction instead of MOVC.

Changing the pointers from generic to typed code seems to have fixed this but we're not sure what to make of this as the spec for the chip clearly states both instructions can be used.

As this been seen before?

Thanks.

[ovrebekk]

Hi

Where is it stated that both instructions can be used?

In the nRF24LE1 I know the XDATA and code memory regions were separate, and you had to use the right instruction, but I see there is no address space overlap between code and XDATA in the nRF24LU1+ so you might be correct.

My memory on the nRF24LU1+ is getting a bit rusty unfortunately, but I can check internally.

Best regards

[NGO]

Hi Torbjørn,

Thank you for following up.

Right: for the LE1, it's quite clear how MOVC and MOVX apply.

In the LU1+ specification 1.1, page 127, figure 16, we can read: "Program/Data (Flash 32 kB) Accessible with movc and movx".

What we have found (but it is an on-going debate internally) is that MOVX is unreliable reading from flash. Mostly it works and by mostly we mean over 99% but there does appear to be a problem.

[ovrebekk]

Hi

What memory addresses are you reading from?

Best regards

[NGO]

Thank you for returning to this topic, Torbjørn.

Originally, the application was using MOVX to read the flash memory at the address range 0x6A00 to 0x73FF.

[ovrebekk]

Hi

The only configuration bits I know of that affect memory access are the INFEN and PMW bits (found in the FSR and PCON registers respectively).

Could you try changing these two and see if it makes a difference?

Best regards