Lpc2000

Below is a draft of a possible sensible formal request we could make 
to Philips with regard to bootloader enhancement. It is simple and 
practical. 

If Philips agrees we can use interrupts by copying interrupt 
instructions and constant addresses to the start of RAM and setting 
MEMMAP to RAM mode. We can still use IAP features of the bootloader. 

There is no sense in replacing the bootloader if you accept it does 
its job as is: why chuck IAP when it works great and can be used to 
advantage in an enhancement, such as with USB enhanced bootloading?

John Heenan


Dear Philips

This is a formal request with regard to the bootloader of the LPC2xxx 
series of microcontrollers.

We are requesting a small enhancement to the bootloader whose end 
functionality is to 
- give us an option to bypass the pin 0.14 test by the bootloader 
when there has been an external reset
- perform our own bootload tasks taking advantage of IAP if we want to
- rejoin the bootloader informing the bootloader what we now want it 
to do or what we have done

For existing LPC2xxx parts with flash based bootloaders we are 
requesting you make an upgrade to the bootloader available to us.

For the bootloader to decide to bypass four items of information are 
necessary
1. Whether to bypass
2. Where to bypass to (in supervisor mode expecting ARM instructions)
3. Where we need to return to if we want to return ('BX LR' is a good 
option)
4. What should be specified in a register on return

On return perhaps R0 could have a value to indicate one of the above

- conduct a normal pin 0.14 test
- bypass pin 0.14 test as if test is true 
- bypass pin 0.14 test as if test was false
- we have used IAP functions to conduct our own bootloading: please 
restart the bootloader as if there was an external reset

Currently address 0x1FC is used to store the CRP value. If this value 
is 0x8765 4321 (or 0x4321 8765) then Code Read Protection (CRP )is 
enabled.

If CRP is not enabled then we request that if the CRP value is 0x4321-
--- or 0x----4321 where ---- represents four hexadecimal digits then 
these hexadecimal digits be used to decide a multiple of 4kB to jump 
to. For example if the CRP value is 0x4321 001E or 0x001E 4321 then 
this is interpreted to call address 0x1E (decimal 30) times 4kB = 
0x0007 B000. This is the start of sector 25 on the LPC2148 and is the 
start of the last 8kB of flash on the LPC2148.

Given that no flash sector can be less than 4kB for erase purposes 
(they are either 4kB or 32kB) then there is no advantage in 
specifying a finer resolution than 4kB as a multiple for call purposes

This request has the support of the following members of the LPC2000 
newsgroup on http://groups.yahoo.com/group/lpc2000/

John Heenan
Add your name if you support such a request!