ARM v7 ADD vs. LDR

Is there any difference between the following instruction (besides flags affection)?

开发者_运维知识库ADD             R6, SP, #0xDC

and

LDR             R6, [SP, #0xDC]

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ADD adds numbers, LDR loads data from memory to registers.

ADD R6, SP, #0xDC   -> R6 = SP + 0xDC
LDR R6, [SP, #0xDC] -> R6 = memory_contents_of_address(SP + 0xDC)