User`s guide

FIR Decimation

5-195

Latency

Zero Latency. The FIR Decimation block has zero tasking latency for all

single-rate operations. The block is single-rate for the particular combinations

of sampling mode and parameter settings shown in the table below.

Note that in sample-based mode, single-rate operation occurs only in the trivial

case of factor-of-1 decimation.

The block also has zero latency for sample-based multirate operations in

Simulink’s single-tasking mode. Zero tasking latency means that the block

propagates the first filtered input sample (received at t=0) as the first output

sample, followed by filtered input samples K+1, 2K+1, and so on.

Nonzero Latency. The FIR Decimation block is multirate for all settings other

than those in the above table. The amount of latency for multirate operation

depends on Simulink’s tasking mode and the block’s sampling mode, as shown

in the table below.

In cases of one-sample latency, a zero initial condition appears as the first

output sample in each channel. The first filtered input sample appears as the

second output sample, followed by filtered input samples K+1, 2K+1, and so on.

In cases of one-frame latency, the first M

output rows contain zeros, where M

is the input frame size. The first filtered input sample (first filtered row of the

input matrix) appears in the output as sample M

+1, followed by filtered input

Sampling Mode Parameter Settings

Sample-based Decimation factor parameter, K, is 1.

Frame-based

Decimation factor parameter, K, is 1, or

Framing parameter is Maintain input frame rate.

Multirate... Sample-Based Latency Frame-Based Latency

Single-tasking

None One frame (M

samples)

Multitasking

One sample One frame (M

samples)