各位大侠，能给我解释下这段代码么？刚接触，看不懂这段代码
// Setup SPI to RAIDAES
PMAPPWD = 0x02D52; // Get write-access to port mapping regs
P1MAP3 = PM_NONE;
P2MAP0 = PM_NONE;
P3MAP2 = PM_UCA0SIMO; // Map UCB0SIMO input to P3.2
P3MAP1 = PM_UCA0SOMI; // Map UCB0SOMI output to P3.1
P3MAP3 = PM_UCA0CLK; // Map UCB0CLK input to P3.3
P3MAP5 = PM_TA1CCR0A; // Map Capture Compare Register to P3.5 to measure CLK_OUT
PMAPPWD = 0; // Lock port mapping registers
