User`s guide

3 Working with Signals
3-10
discrete-time blocks, you may need to interpose a Zero-Order Hold block to
discretize the signal (see the following diagram). Specify the desired sample
period for the signal in the
Sample time parameter of the Zero-Order Hold
block.
The Triggered Signal From Workspace block is also a continuous-time block.
Discrete-Time Source Blocks. Discrete-time source blocks such as Signal From
Workspace require a discrete (nonzero) sample period to be specified in the
block’s
Sample time parameter. Simulink generates an error if a zero value is
specified for the
Sample time parameter of a discrete-time source block.
Nonsource Blocks
All nonsource blocks in the DSP Blockset accept discrete signals, and inherit
the sample period of the input. Others additionally accept continuous-time
discrete signals.
Discrete-Time Nonsource Blocks. Discrete-time nonsource blocks can accept only
discrete-time inputs, and generate only discrete-time outputs. Examples are
all of the resampling and delay blocks, including Upsample and Integer Delay.
A discrete-time nonsource block inherits the sample period and sample rate of
its driving block (the block supplying its input). For example, if the driving
block’s sample period is 0.5 seconds, the inheriting block also executes at 0.5
second intervals. Simulink generates an error if a continuous input is
connected to a discrete-only block.
Continuous/Discrete Nonsource Blocks. In the continuous/discrete blocks,
continuous-time inputs generate continuous-time outputs, and discrete-time
inputs generate discrete-time outputs. Examples are Complex Exponential and
dB Gain. The nonsource triggered blocks such as Triggered Delay Line are also
in this category.
Correct:
Wrong:
Error: Continuous sample
times not allowed for
upsample blocks.