User`s guide

Downsample
5-144
Nonzero Latency. The Downsample block is multirate for most settings other
than those in the above table. The amount of latency for multirate operation
depends on input signal sampling and Simulink’s tasking mode, as shown in
the table below.
The only case of nonzero single-rate latency occurs in sample-based mode,
when
Enforce single rate is selected with D > 0. The latency in this case is one
sample.
In all cases of one-sample latency, the initial condition for each channel appears
as the first output sample. Input sample D+1 appears as the second output
sample for each channel, followed by input sample D+1+K, input sample
D+1+2K, and so on. The
Initial condition parameter can be an M
i
-by-N matrix
containing one value for each channel, or a scalar to be applied to all signal
channels.
In all cases of one-frame latency, the M
i
rows of the initial condition matrix
appear in sequence as the first M
i
output rows. Input sample D+1 (i.e, row D+1
of the input matrix) appears in the output as sample M
i
+1, followed by input
sample D+1+K, input sample D+1+2K, and so on. The
Initial condition value
can be an M
i
-by-N matrix, or a scalar to be repeated across all elements of the
M
i
-by-N matrix. See the example below for an illustration of this case.
See “Excess Algorithmic Delay (Tasking Latency)” on page 3-91 and “The
Simulation Parameters Dialog Box” in the Simulink documentation for more
information about block rates and Simulink’s tasking modes.
Example Construct the frame-based model shown below.
Multirate... Sample-Based Latency Frame-Based Latency
Single-tasking
None, for D=0
One sample, for D>0
One frame (M
i
samples)
Multitasking
One sample One frame (M
i
samples)