DDR and DDR2 SDRAM High-Performance Controller User Guide: question

Could somebody please explain the following from page 4-16 of

the DDR and DDR2 SDRAM High-Performance Controller User Guide:

To map local_wdata and local_be to mem_dq and mem_dm, consider the

following full rate example with 32-bit wide local_wdata and 16-bit wide

mem_dq.

local_wdata = <22334455> <667788AA> <BBCCDDEE>

local_be = <1100> <0110> <1010>

These map to:

mem_dq = <4455> <2233> <88AA> <6677> <DDEE> <BBCC>

mem_dm = <1 1> <0 0> <0 1> <1 0> <0 1> <0 1>

how did they arrive at local_be and mem_dm?

Thanks MikeZ