2.5.1 DMA FIFO

The DMA FIFO is divided into four sections, each one byte wide and 20 transfers deep. The DMA FIFO is illustrated in Figure 2.1.

Figure 2.1 DMA FIFO Sections

32-bits Wide

20

Bytes Deep

8-bits

Byte Lane 3

8-bits

Byte Lane 2

8-bits

Byte Lane 1

8-bits

Byte Lane 0

2.5.1.1 Data Paths

The data path through the LSI53C810A is dependent on whether data is being moved into or out of the chip, and whether SCSI data is being transferred asynchronously or synchronously.

Figure 2.2 shows how data is moved to/from the SCSI bus in each of the different modes.

The following steps determine if any bytes remain in the data path when the chip halts an operation:

2-8

Functional Description

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LSI 53C810A technical manual DMA Fifo, Data Paths