User`s guide

12 Configuring Real-Time Workshop for Your Application

12-4

This figure shows the propagation of the signal attributes associated with the

Inport block through a simple block diagram.

In this example, the Gain and Outport blocks inherit the attributes specified

for the Inport block.

Inherited sample times in source blocks (e.g., a root inport) can sometimes lead

to unexpected and unintended sample time assignments. Since a block may

specify an inherited sample time, often there is not enough information at the

outset to completely compile a block diagram. In such cases, the Simulink

engine propagates the known or assigned sample times to blocks with inherited

sample times which have not yet been assigned a sample time. Thus, it

continues to fill in the blanks, the unknown sample times, until as many blocks

as possible have been assigned a sample time. Blocks which still do not have a

sample time are assigned a default sample time according to the following rule:

1 If the current system has at least one rate in it, the block is assigned the

fastest rate.

2 If no rate exists and the model is configured for a variable-step solver, the

block is assigned a continuous sample time (but fixed in minor time steps).

Note that the Real-Time Workshop does not currently support variable-step

solvers.

3 If no rate exists and the model is configured for a fixed-step solver, the is

assigned a discrete sample time of (T

-T

)/50 where T

is the simulation