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7.4.1.4.1
Normal Mode (MOD = 0)
When an internal frame sync is used, DC[4:0] determine the word transfer rate. In other
words, these bits control how many word periods elapse per frame (although a word is
transferred only during the first period in the frame). The number of word periods per
frame may range from 1 to 32 (DC = 00000 to 11111).
For an external RX or TX frame sync, DC[4:0] define the minimum frame window. Once
the external frame sync triggering edge is received, commencing a new frame, any
additional triggering edges on the same frame sync signal will be ignored, until the
number of word periods defined by DC[4:0] has elapsed during that frame.
Network Mode (MOD = 1; DC ≠ 00000)
7.4.1.4.2
When an internal frame sync is used, DC[4:0] determine the number of time slots per
frame (a separate word will be transferred in each time slot enabled using the
appropriate slot mask register). The number of time slots per frame may range from 2 to
32 (DC = 00001 to 11111). For overview information about Network mode, see Section
7.5.3.2.
For an external RX or TX frame sync, DC[4:0] define the minimum frame window. Once
the external frame sync triggering edge is received, commencing a new frame, any
additional triggering edges on the same frame sync signal will be ignored, until the
number of word periods defined by DC[4:0] has elapsed during that frame.
7.4.1.4.3
On-Demand Mode (MOD = 1; DC = 00000)
In On-demand mode, the frame rate dividers are not used, and periodic frame syncs are
not generated. Instead, a transmit frame sync is output from the DSP as a result of the
core writing a word to an active ESSI transmit register, and one word is shifted in (width
set by CRA(WL[2:0])) on the ESSI serial input pin as a result of a receive frame sync
being input to the DSP. For overview information about On-demand mode, see Section
7.5.3.3.
MOTOROLA
Enhanced Synchronous Serial Interface (ESSI)
DSP56305 User's Manual
ESSI Programming Model
7-17
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