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Designing a bootloader to take application code (led blinking code) from SD/MMC card using SPI and burn in flash of LPC1768 and execute that application code on reset.
This Knowledgebase-article might be helpful: "How to Write a Bootloader"
http://www.keil.com/support/docs/3913.htm
In addition to rkopsch's suggestion, you should be looking to NXP for specific examples & assistance regarding their products.
https://www.nxp.com/products/processors-and-microcontrollers/arm-microcontrollers/general-purpose-mcus/lpc1700-cortex-m3:MC_1403790745385#/
Select your specific chip variant for tools, documentation, etc, etc, ...
There's also mbed:
https://os.mbed.com/platforms/mbed-LPC1768/
https://www.nxp.com/products/processors-and-microcontrollers/arm-microcontrollers/general-purpose-mcus/lpc1700-cortex-m3/arm-mbed-lpc1768-board:OM11043