No the DFU service won't be able to update anything in region 0 if region 0 is defined, ie CLENR0 is set to something other than the default. If you look at the table in the MPU chapter you'll see that ALL has more to do with debugger access to data, code in region 1 can't read or write to the code space in region 0 in any case where CLENR0 is defined.
This is why, since the advent of the Master Boot Record and basic support for DFU, loading the softdevice no-longer sets CLENR0. I think the nRF52 does away with all the region0/region1 stuff and protection is limited to turning the debugger access off.
It's not clear why a readback protection would prevent you from writing? If you could write to region 0 you could clear one page in region 0, write a tiny piece of code to it which dumps the rest of the pages you didn't clear to wherever you like and hence subvert much of the read protection.
The way I interpret the table is that everything (SD, App, BL) is in region 1 not region 0. If CLENR0 is not written then Region 0 Size = 0, and then Region 1 would have to be whats left, which is the entire ROM code memory.
Let UICR.RBPCONF.PALL = 0x00
Let UICR.RBPCONF.PRO = 0xFF
According to Table 40 in section 9.1.3:
If a SWD attempts to access region 1 then all regions are NA0 (Good).
If code in region 1 (i.e. DFU bootloader) requests access then the code/ram region 0 = Limited Access. Since all code is in region 1 then this doesn't matter if my understanding above is correct.
If code in region 1 (i.e. DFU bootloader) requests access then the code/ram region 1 = Full Access. This is good because the SoftDevice, Application, and Bootloader are all in Region 1 if my understanding is correct.
The way I interpret the table is that everything (SD, App, BL) is in region 1 not region 0. If CLENR0 is not written then Region 0 Size = 0, and then Region 1 would have to be whats left, which is the entire ROM code memory.
Let UICR.RBPCONF.PALL = 0x00
Let UICR.RBPCONF.PRO = 0xFF
According to Table 40 in section 9.1.3:
If a SWD attempts to access region 1 then all regions are NA0 (Good).
If code in region 1 (i.e. DFU bootloader) requests access then the code/ram region 0 = Limited Access. Since all code is in region 1 then this doesn't matter if my understanding above is correct.
If code in region 1 (i.e. DFU bootloader) requests access then the code/ram region 1 = Full Access. This is good because the SoftDevice, Application, and Bootloader are all in Region 1 if my understanding is correct.
