Command 1 Register (Dmacmd1); Dma Command 1 Register (Dmacmd1) - Intel 386 User Manual

12.3.5 Command 1 Register (DMACMD1)

Use DMACMD1 to enable both channels and to select the rotating method for changing the bus
control priority structure.
DMA Command 1
DMACMD1
(write only)
7
— —
Bit Bit
Number Mnemonic
7–5 —
4 PRE
3 —
2 CE
1–0 —
Figure 12-22. DMA Command 1 Register (DMACMD1)
— PRE
Reserved; for compatibility with future devices, write zeros to these bits.
Priority Rotation Enable:
0 = Priority is fixed based on value in DMACMD2.
1 = Enables the rotation method for changing the bus control priority
structure. That is, after the external bus master or one of the DMA
channels is given bus control, it is assigned to the lowest priority
level.
Reserved; for compatibility with future devices, write zero to this bit.
Channel Enable:
0 = Enables channel 0 and 1.
1 = Disables the channels.
Reserved; for compatibility with future devices, write zeros to these bits.
DMA CONTROLLER
Expanded Addr: F008H
ISA Addr: 0008H
Reset State: 00H
— CE —
Function
0
—
12-35