Synchronize

Synchronizes two signals.

Library

Description

The Synchronize block synchronizes two signals based on timestamps. The inputs are two signals with their respective timestamps. The Synchronize block outputs the signal values with matching timestamps, including matching timestamps from previous sampling instants. The Maximum history parameter indicates how many previous sampling instants are considered when finding matching timestamps.

The Synchronize block must store previous values of the input signals to match timestamps from prior sampling instants. Hence, for large input signals such as images, be careful not to make the Maximum history parameter too high or the block will consume a large amount of memory unnecessarily.

When a match is found, the output goes high to indicate that the outputs represent a new match. If no match is found then the output goes low and the outputs of the block are left unchanged, holding the last match found.

Multi-dimensional and variable-size signals are supported. Refer to Variable-Size Signals for more details on variable-size signals.

Helpful Hints

Variable-size signals

When using the Synchronize block with variable-size signals in subsystems, make sure any

Input Ports

s1

The first signal. Multi-dimensional and variable-size inputs are supported as well as arbitrary data types.

t1

A scalar input that represents the timestamp for the first signal. Only the Simulink built-in numeric data types are supported. The timestamp need not represent wall-clock time but must be monotonically increasing with time.

s2

The second signal. Multi-dimensional and variable-size inputs are supported as well as arbitrary data types.

t2

A scalar input that represents the timestamp for the second signal. Only the Simulink built-in numeric data types are supported. The timestamp need not represent wall-clock time but must be monotonically increasing with time.

Output Ports

s1

The value of the first signal when the timestamp of the first and second input signal match.

t1

The timestamp of the first signal at the time of the match.

s2

The value of the second signal when the timestamp of the first and second input signal match.

t2

The timestamp of the second signal at the time of the match.

new

A Boolean output indicating whether a match was found. This output goes to one when a match is found during the current sampling instant. Otherwise it is zero.

Data Type Support

The Synchronize block accepts signals of any of the built-in Simulink datatypes, except fixed point, for the signal inputs, s1 and s2. Multi-dimensional and variable-size signals are supported. See Variable-Size Signals for more information on variable-size signals.

The timestamp inputs only accept the built-in Simulink numeric datatypes.

Parameters and Dialog Box

Maximum history

The maximum number of samples of the input to buffer in order to find a match. Note that for large input signals, such as images, the amount of memory used is directly proportional to the magnitude of this parameter.

Threshold for timestamp comparisons

Timestamps may be floating-point or may not represent wall-clock time. Hence, the threshold parameter may be used to indicate what constitutes equality when comparing two timestamps. Formally, two timestamps are considered equal when:

|t1 - t2| <= threhold

Since the comparison is less than or equal to then a threshold value of zero is legitimate. However, for floating-point timestamps, which have inherent inaccuracies, a non-zero threshold such as qc_get_step_size / 2 is recommended.

Targets

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