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Сигнальный МП Motorola DSP56002.pdf
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Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

HOST INTERFACE (HI)

;****************************************

; MAIN PROGRAM... transmit 24-bit data to host

;****************************************

 

ORG

P:$40

 

MOVEP

#1,X:PBC

;Turn on Host Port

MOVEP

#$0C00,X:IPR

;Turn on host interrupt

MOVEP

#0,X:HCR

;Turn off XMT and RCV interrupts

MOVE

#0,SR

;Unmask interrupts

JCLR

#3,X:HSR,*

;Wait for HF0 (from host) set to 1

AND

X0,A

 

JEQ

LOOP

 

MOVEP

#$2,X:HCR

;Enable host transmit interrupt

JMP

*

;Now wait for interrupt

Figure 5-34 Main Program - Transmit 24-Bit Data to Host

;*********************************** ;TRANSMIT to Host Interrupt Routine

;************************************

XMT

MOVEP

#$123456,X:HTX

;Test value to transmit

 

MOVEP

#0,X:HCR

;Turn off XMT Interrupt

RTI

END

Figure 5-35 Transmit to HI Routine

5.3.6.3DMA Data Transfer

The DMA mode allows the transfer of 8-, 16or 24-bit data through the DSP HI under the control of an external DMA controller. The HI provides the pipeline data registers and the synchronization logic between the two asynchronous processor systems. The DSP host exceptions provide cycle-stealing data transfers with the DSP internal or external memory. This technique allows the DSP memory address to be generated using any of the

MOTOROLA PORT B 5 - 55

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

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

HOST INTERFACE (HI)

DSP addressing modes and modifiers. Queues and circular sample buffers are easily created for DMA transfer regions. The host exceptions can be programmed as high priority fast or long exception service routines. The external DMA controller provides the transfers between the DSP HI registers and the external DMA memory. The external DMA controller must provide the address to the external DMA memory; however, the address of the selected HI register is provided by a DMA address counter in the HI.

DMA transfers can only be in one direction at a time; however, the host processor can access any of the registers not in use during the DMA transfer by deasserting HACK and using HEN and HA0-HA2 to transfer data. The host can therefore transfer data in the other direction during the DMA operation using polling techniques.

 

+5 V

 

DMA

1K

DSP56002

CONTROLLER

HOST INTERFACE

TRANSFER REQUEST

 

HREQ

INTERNAL

ADDRESS

COUNTER

TRANSFER

 

HACK

ACKNOWLEDGE

 

 

 

 

MEMORY

H0 - H7

 

 

R/W

CONTROL

ADDRESS DATA

Characteristics of Host DMA Mode

•The HREQ pin is NOT available for host processor interrupts.

•TREQ and RREQ select the direction of DMA transfer.

—DMA to DSP56002

—DSP56002 to DMA

—Simultaneous bidirectional DMA transfers are not permitted.

•Host processor software polled transfers are permitted in the opposite direction of the DMA transfer.

•8-, 16-, or 24-bit transfers are supported.

•16-, or 24-bit transfers reduce the DSP interrupt rate by a factor of 2 or 3, respectively.

Figure 5-36 HI Hardware–DMA Mode

5 - 56 PORT B MOTOROLA

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

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