MSP430 Delay Subroutine
Have a look into section 3.4.4 (Instruction Cycles and Lengths) of the 2xx Family User's Guide (SLAU144):CALL Delay    5 cycles
MOV #x, R10   2 cycles
DEC R10     x*1 cycles
JNZ L1      x*2 cycles
RET           3 cycles (Format-I instruction: MOV @SP+,PC)For 20 ms at 1 MHz, you want 20,000 cycles. Do the math.

Or just let the compiler do the work:

__delay_cycles(20000);