User`s manual

Direct Memory Access

Eight DMA channels are supported by the system. Two Intel 8237-5

DMA controller chips (four channels in each chip) are used to provide

eight DMA channels. The DMA channels are assigned as follows.

CTR 1

CTR 2

CH0 Spare

CH4

Cascade for CTRL 1

CH 1

SDLC

CH5 Spare

CH2

Diskette

CH6

Spare

CH 3

Spare CH7

Spare

Table 6-9: DMA Channels

DMA Channel

Channels 0 through 3 are contained in DMA controller 1. Transfers of

8-bit data, 8-bit I/O adapters and 8-bit or 16-bit system memory are

supported by these channels. Each of these channels will transfer in

64KB blocks throughout the 16-megabyte system address space.

Channels 4 through 7 are contained in DMA controller 2. To cascade

channels 0 through 3 to the microprocessor, use channel 4. Transfers

of 16-bit data between 16-bit adapters and 16-bit system memory are

supported by channels 5, 6 and 7. DMA channels 5 through 7 will

transfer data in 128KB blocks throughout the 16-megabyte system

address space. These channels will not transfer data on odd-byte

boundaries.

Chapter 6: Appendix