急!!急!!急!!MSB&LSB??????????(20分)

请问以下的MSB和LSB是什么意思，作何用的？
(这是ddk中的例子ne2000网卡的驱动)
//
// Offsets from Adapter->IoPAddr of the ports used to access
// the 8390 NIC registers.
//
// The names in parenthesis(括号) are the abbreviations by which
// the registers are referred to in the 8390 data sheet.
//
// Some of the offsets appear more than once
// because they have have relevant page 0 and page 1 values,
// or they are different registers when read than they are
// when written. The notation MSB indicates that only the
// MSB can be set for this register, the LSB is assumed 0.
//
#define NIC_MC_ADDR         0x8     // (MAR0)     page 1
#define NIC_CRDA_LSB        0x8     // (CRDA0)
#define NIC_RMT_ADDR_LSB    0x8     // (RSAR0)
#define NIC_CRDA_MSB        0x9     // (CRDA1)
#define NIC_RMT_ADDR_MSB    0x9     // (RSAR1)
#define NIC_RMT_COUNT_LSB   0xa     // (RBCR0)    write-only
#define NIC_RMT_COUNT_MSB   0xb     // (RBCR1)    write-only

一般情况是
MSB= most significant bit 最高位
LSB= least significant bit 最低位
至于材料的解释，偶就不好瞎说了！

就是高位和低位。