User`s guide

3 Simulink 4.1 Release Notes
3-14
S-Functions Sorted Like Built-In Blocks
When sorting blocks, Simulink now treats S-function blocks the way it treats
built-in blocks. This means that S-functions now work correctly in nonvirtual
subsystems when there is a direct feedback connection (in Simulink 4.0 and
prior, this wasn't the case). It also means that models compile (update
diagram) faster. As a side effect, the execution order for S-functions that
incorrectly set the direct feedthrough flag differs from that used in previous
versions of Simulink. Consequently, models that contain invalid S-functions
may produce different answers in this version of Simulink.
Added Latched Triggered Subsystems
Now triggered subsystems enable you to implement software triggering,
hardware triggering, or a combination of the two. Software triggering is
defined as
if (trigger_signal_edge_detected) {
out(t) = f(in(t));
}
Hardware triggering is defined as
if (trigger_signal_edge_detected) {
out(t) = f(in(t-h)); // h == last step size
}
Previous to this version, triggered subsystems provided software triggering
and a form of hardware triggering when a cycle involving triggered subsystems
existed. Now, you must explicitly specify whether or not you’d like software or
hardware triggering. This is done by selecting
'Latch (buffer) input' on the
Inport blocks in a triggered subsystem.
Each input port of a triggered subsystem configures whether or not the input
should be latched. A latched input provides the hardware-triggering semantics
for that input port. Type
sl_subsys_semantics at the MATLAB prompt for
more information.
Self-Triggering Subsystems Are No Longer Allowed
Before this version, you could define the output of a triggered subsystem to
directly feed back into the trigger port of the subsystem (with potentially other