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Сигнальный МП Motorola DSP56002.pdf
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Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

HOST INTERFACE (HI)

5.3.4.3Host Read/Write (HR/W)

This input selects the direction of data transfer for each host processor access. If HR/W is high and HEN is asserted, H0-H7 are outputs and DSP data is transferred to the host processor. If HR/W is low and HEN is asserted, H0-H7 are inputs and host data is transferred to the DSP. HR/W is stable when HEN is asserted. It can be programmed as a general-purpose I/O pin (PB11) when the host interface is not being used, and is configured as a GPIO input pin during hardware reset.

5.3.4.4Host Enable (HEN)

This input enables a data transfer on the host data bus. When HEN is asserted and HR/W is high, H0–H7 become outputs and the host processor may read DSP56002 data. When HEN is asserted and HR/W is low, H0–H7 become inputs. When HEN is deasserted, host data is latched inside the DSP. Normally, a chip select signal derived from host address

decoding and an enable clock are used to generate HEN. HEN can be programmed as a general-purpose I/O pin (PB12) when the host interface is not being used, and is configured as a GPIO input pin during hardware reset.

5.3.4.5Host Request (HREQ)

This open-drain output signal is used by the DSP56002 HI to request service from the host processor, DMA controller, or a simple external controller. HREQ may be connected to an interrupt request pin of a host processor, a transfer request of a DMA controller or a control input of external circuitry. HREQ is asserted when an enabled request occurs in the host interface. HREQ is deasserted when the enabled request is cleared or masked, DMA

HACK is asserted, or the DSP is reset. HREQ may be programmed as a general purpose I/O pin (not open-drain) called PB13 when the HI is not being used.

5.3.4.6Host Acknowledge (HACK)

The Port B Control register allows the user to program this input independently of the other Host Interface pins. When the port is defined for general purpose I/O, this input acts

 

 

 

Table 5-6 Port B Pin Definitions

 

 

 

 

 

 

BC0

BC1

Function

 

 

 

 

 

 

 

 

 

 

0

0

Parallel I/O (Reset Condition)

01 Host Interface

10 Host Interface (HACK is defined as general purpose I/O)

1

1

Reserved

MOTOROLA PORT B 5 - 33

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