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Сигнальный МП Motorola DSP56002.pdf
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Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

HOST INTERFACE (HI)

as a general purpose I/O pin called PB14. When the port is defined as the host interface, the user may manipulate the Port B Control register to program this input as either PB14, or as the HACK pin. The table below shows the Port B Control register bit configurations.

HACK may act as a data strobe for HI DMA data transfers (See Figure 5-18). Or, if HACK is used as an MC68000 host interrupt acknowledge, it enables the HI interrupt vector register (IVR) on the host data bus H0-H7 if HREQ is asserted (See Figure 5-16). In this case, all other HI control pins are ignored and the state of the HI is not affected.

Note: HACK should always be pulled high when it is not in use.

5.3.5Servicing the Host Interface

The HI can be serviced by using one of the following protocols:

1.Polling

2.Interrupts, which can be either

a.non-DMA

b.DMA

From the host processor viewpoint, the service consists of making a data transfer since this is the only way to reset the appropriate status bits.

 

DSP56002

 

3

HA0 - HA2

HA0 - HA2

HR/W

 

HR/W

 

 

HEN

 

HEN

 

 

H0 - H7

 

8

 

H0 - H7

 

 

+5 V

WRITE

DATA

READ

 

LATCHED

 

 

IN HI

HREQ

 

 

 

 

+5 V

 

 

HACK

Figure 5-15 Host Processor Transfer Timing

5 - 34 PORT B MOTOROLA

For More Information On This Product, Go to: www.freescale.com

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