7-42
DSP56309UM/D MOTOROLA
Enhanced Synchronous Serial Interface (ESSI)
Operating Modes
¥ When the FSR bit is set, the word length frame sync is generated (or expected)
with the last bit of the previous word.
FSR is ignored when a bit length frame sync is selected.
7.5.4.3.4
Frame Sync Polarity
The FSP bit controls the polarity of the frame sync.
¥ When the FSP bit is cleared, the polarity of the frame sync is positive (i.e., the
frame sync signal is asserted high). The ESSI synchronizes on the leading edge of
the frame sync signal.
¥ When the FSP bit is set, the polarity of the frame sync is negative (i.e., the frame
sync is asserted low). The ESSI synchronizes on the trailing edge of the frame sync
signal.
The ESSI receiver looks for a receive frame sync edge (leading edge if FSP is cleared,
trailing edge if FSP is set) only when the previous frame is completed. If the frame sync
is asserted before the frame is completed (or before the last bit of the frame is received in
the case of a bit frame sync or a word length frame sync with FSR set), the current frame
sync is not recognized, and the receiver is internally disabled until the next frame sync.
Frames do not have to be adjacent, that is, a new frame sync does not have to follow
immediately the previous frame. Gaps of arbitrary periods can occur between frames.
All the enabled transmitters are tri-stated during these gaps.
7.5.4.4
Byte Format (LSB/MSB) for the Transmitter
Some devices, such as codecs, require a MSB-first data format. Other devices, such as
those that use the AES-EBU digital audio format, require the LSB first. To be compatible
with all formats, the shift registers in the ESSI are bidirectional. The MSB/LSB selection
is made by programming the SHFD bit in the CRB.
¥ If the SHFD bit is cleared, data is shifted into the receive shift register MSB first
and shifted out of the transmit shift register MSB first.
¥ If the SHFD bit is set, data is shifted into the receive shift register LSB first and
shifted out of the transmit shift register LSB first.
7.5.5
Flags
Two ESSI signals (SC[1:0]) are available for use as serial I/O flags. Their operation is
controlled by the SYN, SCD[1:0], SSC1, and TE[2:1] bits in the CRB/CRA.The control bits
OF[1:0] and status bits IF[1:0] are double-buffered to/from SC[1:0]. Double-buffering the
flags keeps the flags in sync with TX and RX.
Summary of Contents for DSP56309
Page 25: ...xxii DSP56309UM D MOTOROLA Figure D 25 Port E Registers PCRE PRRE PDRE D 39 ...
Page 30: ...MOTOROLA DSP56309UM D 1 1 SECTION 1 DSP56309 OVERVIEW ...
Page 47: ...1 18 DSP56309UM D MOTOROLA DSP56309 Overview DSP56309 Architecture Overview ...
Page 48: ...MOTOROLA DSP56309UM D 2 1 SECTION 2 SIGNAL CONNECTION DESCRIPTIONS ...
Page 85: ...2 38 DSP56309UM D MOTOROLA Signal Connection Descriptions OnCE JTAG Interface ...
Page 86: ...MOTOROLA DSP56309UM D 3 1 SECTION 3 MEMORY CONFIGURATION ...
Page 104: ...MOTOROLA DSP56309UM D 4 1 SECTION 4 CORE CONFIGURATION ...
Page 124: ...MOTOROLA DSP56309UM D 5 1 SECTION 5 GENERAL PURPOSE I O ...
Page 125: ...5 2 DSP56309UM D MOTOROLA General Purpose I O 5 1 INTRODUCTION 5 3 5 2 PROGRAMMING MODEL 5 3 ...
Page 128: ...MOTOROLA DSP56309UM D 6 1 SECTION 6 HOST INTERFACE HI08 ...
Page 166: ...MOTOROLA DSP56309UM D 7 1 SECTION 7 ENHANCED SYNCHRONOUS SERIAL INTERFACE ESSI ...
Page 212: ...MOTOROLA DSP56309UM D 8 1 SECTION 8 SERIAL COMMUNICATION INTERFACE SCI ...
Page 241: ...8 30 DSP56309UM D MOTOROLA Serial Communication Interface SCI GPIO Signals and Registers ...
Page 242: ...MOTOROLA DSP56309UM D 9 1 SECTION 9 TRIPLE TIMER MODULE ...
Page 269: ...9 28 DSP56309UM D MOTOROLA Triple Timer Module Timer Operational Modes ...
Page 270: ...MOTOROLA DSP56309UM D 10 1 SECTION 10 ON CHIP EMULATION MODULE ...
Page 302: ...MOTOROLA DSP56309UM D 11 1 SECTION 11 JTAG PORT ...
Page 369: ...C 22 DSP56309UM D MOTOROLA DSP56309 BSDL Listing ...
Page 370: ...MOTOROLA DSP56309UM D D 1 APPENDIX D PROGRAMMING REFERENCE ...
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