TMS320AV7110 datasheet(70/131 Pages) TI

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DSP

TMS320AV7110

Revision 3.1

10/08/99 22:18

Page 70

13.2 External DMA Interface

When configured for External DMA (EDMA) operation (HSDI_STATUS[1:0] = 01), the HSDI is

capable of being connected directly to an external data processing device. One example of this is an

Enhanced SCSI Controller (ESC) device such as the NCR 53CF94-1/53CF96-1. Figure 26 illustrates

the connections for this example configuration.

SCSI

Contr

oller

NCR 53CF94/53CF96

DMAWR

DMA[15-8]

DREQ

DACK

CLK

10-40 MHz

INT

EXTINT2

EDMA_DB[7:0]

EDMA_A[3:0]

A[3:0]

DMA[7:0]

EDMA_DREQ

EDMA_DACK

EDMA_CS

EDMA_WR

‘AV7110

AD[7-0]

EDMA_RD

Mode[1:0]

Figure 26. Interfacing the ‘AV7110 to a SCSI chip

Because there is only an 8-bit bus on the HSDI, the ESC is limited to an 8-bit, Single Bus Architecture

so it’s mode selection inputs should be set to mode 0. The upper data bits can be left floating because

they have internal pull-ups on the ESC. Likewise, the AD7-0 inputs of the ESC will not be used for this

mode and can be left unconnected. Note that the ESC requires an external clock source from 10 MHz

to 40 MHz. Because the CLK40 signal of the ‘Av7110 is actually a 40.5 MHz clock it should not be

used directly for this Controller without violating it’s specification. Table 36 shows the signals needed

for the EDMA interface.

Table 36. External DMA Interface Signals

Signals

I/O

Description

EDMA_DB[7:0]

In/Out

External Controller data bus.

EDMA_A[3:0]

Out

External Controller register select.

EDMA_WR

Out

Write signal. (Active Low)

EDMA_RD

Out

Read signal. (Active Low)

EDMA_DREQ

DMA request signal. *

EDMA_DACK

Out

DMA Data strobe select *

EDMA_CS

Out

Chip select for External Controller

(Active Low)

* The polarity of these signals is selectable by a user callable API and defaults to active Low

With the ‘AV7110 configured for External DMA operation on the HSDI, data can be transferred at a

maximum data rate of 5MBytes/sec. Interfacing to the HSDI DMA is done through API and so data

transfer is under firmware control. Specific data formats such as the Enhanced SCSI Controller (ESC)

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