Associates a DMA channel with an alternate map register set.
Call with:
AH = 5BH
AL = 06H
BL = alternate map register set
DL = DMA channel number
Returns:
If function successful
AH = 00H
If function unsuccessful
AH = error code
Notes:
If a DMA channel is not assigned to a specific register set, DMA for that channel will be mapped through the current register set.
If zero is specified as the alternate map register set, no special action is taken on DMA accesses for the specified DMA channel.
This function is intended for use by operating systems only and can be disabled by the operating system at any time.