Acrosser AR-B9612 - Manual (Page 7)

2-2 AR-B9612 User’s Guide
2.2 DMA CONTROLLER
The equivalent of two 8237A DMA controllers are implemented
in the AR-B9612 card. Each controller is a four channel DMA
device which will generate the memory addresses and control
signals necessary to transfer information directly between a
peripheral device and memory. This allows high speed
information transfer with less CPU intervention. The two
DMA controllers are internally cascaded to provide four DMA
channels for transfers to 8-bit peripherals (DMA1) and three
channels for transfers to 16-bit peripherals (DMA2). DMA2
channel 0 provides the cascade interconnection between the two
DMA devices, thereby maintaining IBM PC/AT compatibility.
Following is the system information of DMA channels:
DMA Controller 1 DMA Controller 2
Channel 0: Spare Channel 4: Cascade for controller 1
Channel 1: IBM SDLC Channel 5: Spare
Channel 2: Diskette adapter Channel 6: Spare
Channel 3: Spare Channel 7: Spare
Table 2-1 DMA Channel Controller