Lpc2000

> 1) Do I need to erase the flash before programming it?

In most cases, yes. It is best to erase the flash area u want before 
writing new a new program to it. Note that u can successfully write 
data to flash without an erase but there's a limit to the number of 
writes u can use in between erases.

> 2) Does the "prepare for write" command just unlock the flash or 
does it erase the flash too?

Prepare only unlocks the flash

> 3) If I wish to program using partial pages (let's say 64 bytes at
> a time), is the following the way to do it?
> 
>   prepare for write
>   erase block
>   prepare for write
>   write first partial page
>   prepare for write
>   write second partial page
>   ......
>  Where the partial page programming means writing 512 bytes all 
0xFF 
> except for the bytes I intend writing (as per msg 2999).

The minimum page size allowable during reads/writes is 512 bytes, 
and goes up to 8192 bytes. 
U can only erase 1 sector at a time, and each sector is usually 8192 
bytes (16 pages). 

Revise the IAP routines in the chapter "Flash Memory System & 
Programming" of your lpc Usr manual for more details. 

Leighton