Hi Sudarshan S,
Read the flash memory is very easy, just read the according flash address and get the data is OK, you don't need to use the flash operation command.
But the write, you need to use the flash IAP command, you can find it from the LPC11C24 user manual:

About the code, you can refer to the secondary bootloader, which can be downloaded from this link:
AN10995: LPC1100 secondary bootloader (with software) (v.1.3) | www.LPCware.com
Folder:AN10995 LPC1100 secondary bootloader (with software)\AN10995\Bootloader

When you do the flash operation, don't let other module's interrupt to break the flash operation.
Wish it helps you!
If you still have question, please let me know!
Have a great day,
Kerry
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