Motorola DSP56011 User Manual Download

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MOTOROLA

DSP56011 User’s Manual

8-1

SECTION 8

DIGITAL AUDIO TRANSMITTER

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Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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Summary of Contents for DSP56011

Page 1: ...MOTOROLA DSP56011 User s Manual 8 1 SECTION 8 DIGITAL AUDIO TRANSMITTER Freescale Semiconductor I Freescale Semiconductor Inc For More Information On This Product Go to www freescale com nc ...

Page 2: ...8 3 8 2 DAX SIGNALS 8 4 8 3 DAX FUNCTIONAL OVERVIEW 8 5 8 4 DAX PROGRAMMING MODEL 8 6 8 5 DAX INTERNAL ARCHITECTURE 8 6 8 6 DAX PROGRAMMING CONSIDERATIONS 8 14 Freescale Semiconductor I Freescale Semiconductor Inc For More Information On This Product Go to www freescale com nc ...

Page 3: ...in Slave or Master mode Supports both Master mode and Slave mode in a digital audio network If the user selects a divided DSP core clock the DAX will operate in the Master mode If the user selects an external clock source the DAX will operate in the Slave mode The accessible DAX registers are all mapped in the X I O memory space This allows programmers to access the DAX using standard instructions...

Page 4: ...384 times or 512 times the audio sampling frequency 256 Fs 384 Fs or 512 Fs The ACI pin is high impedance during hardware reset and software reset Note If the DAX is not used connect the ACI pin to ground through an external pull down resistor to ensure a stable logic level at the input Figure 8 1 Digital Audio Transmitter DAX Block Diagram XADRB 0 23 XADBUF MUX 26 XSTR C U V PRTYG Biphase Encoder...

Page 5: ...ent to the DSP core The interrupt handling routine then stores the next frame of audio data in the XADRA XADRB and the non audio data bits in the XCTR At the beginning of a frame transmission one of the 8 bit Channel A preambles Z preamble for the first sub frame in a block or X preamble otherwise is generated in the preamble generator and then shifted out to the ADO pin in the first eight time sl...

Page 6: ...re uploaded 8 4 DAX PROGRAMMING MODEL The programmer accessible DAX registers are shown in Figure 8 2 on page 8 7 The registers are described in the following subsections The Interrupt Vector table for the DAX is shown in Table 8 1 The internal interrupt priority is shown in Table 8 2 8 5 DAX INTERNAL ARCHITECTURE Hardware components shown in Figure 8 1 on page 8 4 are described in the following s...

Page 7: ...nnel A audio and non audio data are being transmitted At the beginning of a frame transmission audio data stored in the XADRA is directly transferred to the XADSR for Channel A transmission and at the same time the Channel B audio data stored in XADRB is transferred to the XADBUF The Channel B audio data in the XADBUF is transferred to the XADSR at the beginning of the Channel B transmission This ...

Page 8: ...frame The contents of the XCTR are shown in Figure 8 2 on page 8 7 The XCTR bits are described in the following paragraphs 8 5 4 1 DAX Enable XEN Bit 0 When the XEN bit is set the DAX is enabled If the DAX Stop XSTP control bit is set XEN is sampled at every frame boundary thus clearing XEN during the middle of a frame transmission will stop transmission at the next frame boundary If XSTP is clear...

Page 9: ...AX reset states 8 5 4 7 DAX Channel A User Data XUA Bit 11 The value of the XUA bit is transmitted as the thirtieth bit Bit 29 of the Channel A sub frame in the next frame Note This bit is not affected by any of the DAX reset states 8 5 4 8 DAX Channel A Channel Status XCA Bit 12 The value of the XCA bit is transmitted as the thirty first bit Bit 30 of the Channel A sub frame in the next frame Not...

Page 10: ...very frame transmission more precisely when an audio data upload from the XADRA XADRB to XADSR XADBUF occurs When XADE is set and the DAX interrupt is enabled XIEN 1 a DAX interrupt request with the Transmit Data Empty interrupt vector is sent to the DSP core Note XADE is cleared by writing data to XADRA and XADRB It is cleared by software reset and hardware reset and by the Stop state 8 5 5 2 XST...

Page 11: ...rogress XTIP Bit 4 The XTIP status flag indicates that the DAX is enabled and transmitting data When XTIP is set it indicates that the DAX is active When XTIP is cleared it indicates that the DAX is inactive This bit provides programmers with the means to determine whether the DAX is active or inactive Since the DAX can be active and transmitting data even after the XEN bit in the XCTR has been cl...

Page 12: ...ame being transmitted The generated parity bit ensures that sub frame bits four to thirty one will carry an even number of 1s and 0s 8 5 8 DAX Biphase Encoder The DAX biphase encoder encodes each audio and non audio bit into its biphase mark format and shifts this encoded data out to the ADO output pin synchronous to the biphase clock 8 5 9 DAX Preamble Generator The DAX preamble generator automat...

Page 13: ...nd generates the biphase clock 128 Fs and shift clock 64 Fs The clock source can be selected from the following options see also Section 8 5 4 4 on page 8 9 The internal DSP core clock assumes 1024 Fs DAX clock input pin ACI 512 Fs DAX clock input pin ACI 384 Fs DAX clock input pin ACI 256 Fs Figure 8 5 shows how each clock is divided to generate the biphase and bit shift clocks Figure 8 4 Preambl...

Page 14: ... Interrupt Handling When the XIEN bit is set and the DAX is active a Transmit Audio Data register Empty interrupt XADE 1 is generated once at the beginning of every frame transmission Typically within an XADE interrupt one frame of audio data to be transmitted in the next frame is stored in the XADRA and the XADRB by two consecutive MOVEP instructions within a fast interrupt routine This clears th...

Page 15: ...active While the DSP is in the Stop state the DAX will remain in the individual reset state and the status flags are initialized as described for resets No DAX control bits are affected It is recommended that the DAX be disabled by clearing the XEN bit in the XCTR before the DSP enters the Stop state Freescale Semiconductor I Freescale Semiconductor Inc For More Information On This Product Go to w...

Page 16: ...DSP56011 User s Manual MOTOROLA Digital Audio Transmitter DAX Programming Considerations Freescale Semiconductor I Freescale Semiconductor Inc For More Information On This Product Go to www freescale com nc ...

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