Check for proper Merge block usage

Condition

Recommended Action

Merge blocks can be interconnected to form

Rework your model so that no

a tree structure.

blocks drive the same tree of

Merge blocks.

Condition

Recommended Action

Check the run-time diagnostic

setting of the Merge block.

1 In the Configuration Parameters

dialog box, on the Diagnostics >

Data Validity pane, set “Detect

multiple driving blocks executing

at the same time step” to error.

2 Verify that the model simulates

without errors before running this

check again.

Verify that Model blocks are using

Migrate the model referenced by

the simplified initialization mode.

the Model block to the simplified

initialization mode, then migrate the

top model.

Check for Model blocks that are

The simplified initialization

using the PIL simulation mode.

mode does not support the

Processor-in-the-loop (PIL)

simulation for model references.

Condition

Recommended Action

Check for single-input Merge blocks.

Replace both the Mux block used

to produce the input signal and the

Merge block with one multi-input

Merge block. Single-input Merge

blocks are not supported in the

simplified initialization mode.

Check for root Merge blocks that

Specify an explicit value for the

have an unspecified ’Initial output’.

Initial output parameter of root

Merge blocks. A root Merge block is

a Merge block with an output port

that does not connect to another

Merge block.

Check for Merge blocks with nonzero

Clear the Allow unequal port

input port offsets.

widths parameter of the Merge

block.

Note Consider using Merge blocks

only for signal elements that require

true merging. You can combine other

elements with merged elements

using the Concatenate block.

Check for Merge blocks that have

Set the Number of inputs

unconnected inputs or that have

parameter of the Merge block to the

inputs from non-conditionally

number of Merge block inputs. You

executed subsystems.

must connect each input to a signal.

Verify that each Merge block input

is driven by a conditionally executed

subsystem. Merge blocks cannot

be driven directly by an Iterator

Subsystem or a block that is not a

conditionally executed subsystem.

Condition

Recommended Action

Check for Merge blocks with inputs

Verify that any combination or

that are combined or reordered

reordering of Merge block input

outside of conditionally executed

signals takes place within a

subsystems.

conditionally executed subsystem.

Such designs may use Mux, Bus

Creator, or Selector blocks.

Check for Merge blocks with

Verify that input signals to each

inconsistent input sample times.

Merge block have the same Sample

time.

Failure to do so could result

in unpredictable behavior.

Consequently, the simplified

initialization mode does not allow

inconsistent sample times.

Check for Merge blocks with multiple

Verify that the Merge block does not

input ports that are driven by a

have multiple input signals that are

single source.

driven by the same conditionally

executed subsystem or conditionally

executed Model block.

Check for Outport blocks that

The Outport block has a function-call

have conflicting signal buffer

trigger or function-call data

requirements.

dependency signal passing through

it, along with standard data

signals. Some of the standard data

signals require an explicit signal

buffer for the initialization of the

output signal of the corresponding

subsystem. However, buffering

function-call related signals leads

to a function-call data dependency

violation.

Consider modifying the model

to pass function-call related

signals through a separate

Outport block. For examples of

function-call data dependency

Condition

Recommended Action

violations, see the example model

sl_subsys_semantics.

A standard data signal may require

an additional signal copy for one of

the following reasons:

• The Outport block is driven by

a block with output that cannot

be overwritten. The Ground

block and the Constant block are

examples of such blocks.

• The Outport block shares the

same signal source with another

Outport block in the same

subsystem or in one nested within

the current subsystem but having

a different initial output value.

• The Outport block connects to the

input of a Merge block

• One of the input signals of the

Outport block is specifying a

Simulink.Signal object with an

explicit initial value .

Check for Outport blocks that

An explicit copy of the bus signal

require an explicit signal copy.

driving the Outport block is

required for the initialization of the

output signal of the corresponding

subsystem. Insert a Signal

Conversion block before the

Outport block, then set the Output

parameter of the Signal Conversion

block to Bus copy.

A standard data signal may require

an additional signal copy for one or

more of the following reasons:

Condition

Recommended Action

• A block with output that cannot be

overwritten is driving the Outport

block. The Ground block and the

Constant block are examples of

such blocks.

• The Outport block shares the

same signal source with another

Outport block in the same

subsystem or in one nested within

the current subsystem but having

a different initial output value.

• The Outport block connects to the

input of a Merge block

• One of the input signals of the

Outport block is specifying a

Simulink.Signal object with an

explicit initial value.

Check for merged Outport

Determine if the new behavior of the

blocks that are driven by nested

Outport blocks is acceptable. If it

conditionally executed subsystems.

is not acceptable, modify the model

to account for the new behavior

before migrating to the simplified

initialization mode.

Check for merged Outport blocks

Set the Output when disabled

that reset when the blocks are

parameter of the Outport block

disabled.

to held. This setting is required

because the Outport block connects

to a Merge block.

For more information, see Outport.

Condition

Recommended Action

Check for Outport blocks that have

Specify the Initial output

an undefined ’Initial output’ value.

parameter for the Outport block,

unless you want the block to obtain

its Initial output value from its

input signal.

If you want the Outport block to

obtain its Initial output value

from its input signal, verify that its

sources are valid. For the simplified

initialization mode, valid sources

from which an Outport blocks can

inherit Initial output value are:

Constant, Initial Condition, Merge

(with initial output), or conditionally

executed subsystem blocks.

Note If you are working with a

conditionally executed subsystem

Outport block, driven directly by

another conditionally executed

subsystem Outport block, then

resolve this error message for

the inner Outport block first.

Subsequently, run this Model

Advisor check again to determine

if you resolved the problem for the

outer Outport block.

Condition

Recommended Action

Check Outport blocks that have

Simulink has inserted a Rate

automatic rate transitions.

Transition block at the input of the

Outport block. If this rate transition

is required, then specify the Initial

output parameter for each Outport

block.

Otherwise, perform the following

procedure:

1 In the Configuration Parameters

dialog box, on the Solver pane,

clear the option “Automatically

handle rate transition for data

transfer”.

2 Run this Model Advisor check

again.

Check Outport blocks that have a

Specify the Initial output

special signal storage requirement.

parameter for the Outport block.

The Outport block cannot obtain

Initial output values from its input

signals because of its special internal

signal storage requirement.

Check the ’Initial output’ setting of

Specify the Initial output

Outport blocks that reset when they

parameter of the Outport block.

are disabled.

You must specify the Initial output

value for blocks that are configured

to reset when they become disabled.

Condition

Recommended Action

Check the ’Initial output’ setting for

You cannot specify an Initial

Outport blocks that pass through

output value for the Outport

a function-call data dependency

block because function-call data

signal.

dependency signals are passing

through it. To set the Initial output

value:

1 Set the Initial output parameter

of the Outport block to [].

2 Provide the initial value at the

source of the data dependency

signal rather than at the Outport

block.

Check for blocks inside of the

Within an Iterator Subsystem

Iterator Subsystem that require

hierarchy, do not use blocks that

elapsed time.

require a service that maintains the

time that has elapsed between two

consecutive executions.

Since an Iterator Subsystem can

execute multiple times at a given

time step, the concept of elapsed

time is not well-defined between two

such executions. Using these blocks

inside of an Iterator Subsystem can

cause unexpected behavior.

Condition

Recommended Action

Check for Outport blocks that use

Verify that the following behavior is

signal objects to specify the ’Initial

acceptable.

output’ value.

In the simplified initialization mode,

signal objects cannot specify the

Initial output parameter of an

Outport block. You can still initialize

the input or output signals for an

Outport block using signal objects,

but the initialization results may be

overwritten by those of the Outport

block.

Note If you are working with a

conditionally executed subsystem

Outport block, Simulink generates a

warning that the initial value of the

signal object has been ignored.

Check for merged Outport blocks

Verify that the following behavior is

that are either unconnected or

acceptable.

connected to a Ground block.

The Outport block is driving a

Merge block, but its inputs are

either unconnected or connected

to Ground blocks. In the classic

initialization mode, unconnected or

grounded outports do not update the

merge signal even when their parent

conditionally executed subsystems

are executing. In the simplified

initialization mode, however, these

outports will update the merge

signal with a value of zero when

their parent conditionally executed

subsystems are executing.

Condition

Recommended Action

Check for Merge blocks that use

Verify that the following behavior is

signal objects to specify the ’Initial

acceptable.

output’ value.

In the simplified initialization mode,

signal objects cannot specify the

Initial output parameter of the

Merge block. While you can still

initialize the output signal for a

Merge block using a signal object,

the initialization result may be

overwritten by that of the Merge

block.

Note Simulink generates a warning

that the initial value of the signal

object has been ignored.

Check for Outport blocks that obtain

Verify that the following behavior is

the ’Initial output’ value from an

acceptable.

input signal when they are migrated.

The Initial output parameter of the

Outport block is not specified. As a

result, the simplified initialization

mode will assume that the Initial

output value for the Outport block

is derived from the input signal. This

assumption may result in different

initialization behavior.

If this behavior is not acceptable,

modify your model before

you migrate to the simplified

initialization mode.

Condition

Recommended Action

Check for innermost Outport blocks

In classic initialization mode,

with variable-size input and an

Simulink assumes that the ’Initial

unspecified ’Initial output’.

output’ parameter is 0 when it is

unspecified ([]) for the innermost

Outport block. This block has

variable-size input for which the

signal size varies only when the

parent subsystem is re-enabled.

Unless you specify the value of

the Initial output parameter,

it will be set to zero when your

model is migrated to the simplified

initialization mode.

Check for outer Outport blocks that

Verify that the following behavior is

have an explicit ’Initial output’.

acceptable.

In the classic initialization mode,

the Initial output and Output

when disabled parameters of the

Outport block must match those of

their source Outport blocks.

Consequently, Simulink will set

the ’Source of initial output value’

parameter to ’Input signal’ in the

simplified initialization mode.

Check for conditionally executed

Verify that the following behavior is

subsystems that propagate execution

acceptable.

context across the output boundary.

The Propagate execution context

across subsystem boundary

parameter is selected for the

subsystem. Execution context

will still be propagated across

input boundaries; however, the

propagation will be disabled on the

output side for the initialization in

the simplified initialization mode.

Condition

Recommended Action

Check for Discrete-Time Integrator

Verify that the following behavior is

blocks.

acceptable.

Simulink has changed the

initialization behavior of the

Discrete-Time Integrator block to be

more consistent and robust in the

simplified initialization mode. These

changes include:

• Elimination of the Use initial

condition as initial and reset

value for parameter

• Application of the Initial

condition parameter only to the

integrator output

• Simplified enable/disable

behavior.

See the Discrete-Time Integrator

block documentation for more

information on the simplified

initialization for the Discrete-Time

Integrator.

Check for blocks that read input from

Verify that the following behavior is

conditionally executed subsystems

acceptable.

during initialization.

Some blocks, such as the

Discrete-Time Integrator block,

read their inputs from conditionally

executed subsystems during

initialization in the classic

initialization mode. Simulink

performs this step as an optimization

technique.

This optimization is not allowed in

the simplified initialization mode

Condition

Recommended Action

because the output of a conditionally

executed subsystem at the first

time step after initialization may

be different than the initial value

declared in the corresponding

Outport block. In particular, this

discrepancy occurs if the subsystem

is active at the first time step.

Check for library blocks with

Examine the failed subcheck results

instances that cannot be migrated.

for each block to determine the

corrective actions.

Check for library blocks with

Examine the warning subcheck

instances that have warnings.

results for each block before

migrating to the simplified

initialization mode.

Check for a migration conflict for

Other instances of Outport blocks

Outport blocks that will use a

with the same library link either

’Dialog’ as the ’Source of initial

cannot be migrated or are being

output value’.

migrated in a different manner.

Review the results from the Check

for library blocks with instances

that cannot be migrated to learn

about the different migration paths

for other instances of each Outport

block.

The Outport block will maintain its

current settings and use its specified

Initial output value.

Condition

Recommended Action

Check for a migration conflict for

Other instances of Outport blocks

Outport blocks that will use an

with the same library link either

’Input signal’ as the ’Source of initial

cannot be migrated or are being

output’ value.

migrated in a different manner.

Review the results from the Check

for library blocks with instances

that cannot be migrated to learn

about the different migration paths

for other instances of each Outport

block.

The Outport block currently specifies

an Initial output of [] (empty

matrix), and the Output when

disabled as held. This means

that each outport does not perform

initialization, but implicitly relies on

source blocks to initialize its input

signal.

After migration, the parameter

Source of initial output value

will be set to Input signal to reflect

this behavior.

Check for a migration conflict for

Other instances of Outport blocks

Outport blocks that have SimEvents

with the same library link either

semantics.

cannot be migrated or are being

migrated in a different manner.

Review the results from the Check

for library blocks with instances

that cannot be migrated to learn

about the different migration paths

for other instances of each Outport

block.

The Outport blocks will continue

to use an Initial output value of

[] (empty matrix) and an Output

when disabled setting of held.