TDM Mode
C-6 ADSP-214xx SHARC Processor Hardware Reference
Programs have control over various attributes of this mode. One attribute
is the number of bits (8- to 32-bit word lengths). However, each sample of
the pair that occurs on each frame sync must be the same length.
TDM Mode
Many applications require multiple I/O channels to implement the
desired system functions (such as telephone line and acoustic interfaces).
Because most DSPs provide one, or at most two SPORTs, and one of
these may be required for interfacing to the host or supervisory processor,
it may be impractical, if not impossible, to dedicate a separate SPORT
interface to each AFE connection.
The solution is to devise a way to connect a series of serial devices to one
SPORT. Different converter manufacturers have approached this task in
different ways. In essence, though, there are only two choices; either a
time division multiplexing (TDM) approach, where each device is active
on the SPORT in a particular time slot, or a cascading approach, where all
devices are daisy chained together and data is transferred by shifting it
through the chain and then following with a latching signal or a serial pro-
tocol. Figure C-1 illustrates a pulsed frame clock for the TDM operation.
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