User`s guide

Delay and Latency
3-91
Excess Algorithmic Delay (Tasking Latency)
Under certain conditions, Simulink may force a block to delay inputs longer
than is strictly required by the block’s algorithm. This excess algorithmic delay
is called tasking latency, because it arises from synchronization requirements
of Simulink’s tasking mode. A block’s overall algorithmic delay is the sum of its
basic delay and tasking latency.
Algorithmic delay = Basic algorithmic delay + Tasking latency
The tasking latency for a particular block may be dependent on the following
block and model characteristics:
•Simulink tasking mode
•Block rate type
•Model rate type
•Block sample mode
Simulink Tasking Mode. Simulink has two tasking modes:
•Single-tasking
•Multitasking
Select a mode by choosing
SingleTasking or MultiTasking from the Mode
pop-up menu in the
Solver panel of the Simulation Parameters dialog box.
The
Mode pop-up menu is only available when the Fixed-step option is
selected from the
Type pop-up menu. (When the Variable-step option is
selected from the
Type pop-up menu, Simulink always operates in
single-tasking mode.) The
Auto option in the Mode pop-up menu automatically
selects single-tasking operation if the model is single-rate (see below), or
multitasking operation if the model is multirate.
Many multirate blocks have reduced latency in Simulink’s single-tasking mode;
check the “Latency” section of a multirate block’s reference page for details.
Also see “The Simulation Parameters Dialog Box” in the Simulink
documentation for more information about the tasking modes and other
simulation options.
Block Rate Type. A block is called single-rate when all of its input and output
ports operate at the same frame rate (as indicated by identical Probe block
measurements or sample time color coding on the input and output lines). A