Digital Input

Select and connect digital input lines or channels


Real-Time Windows Target™


The Digital Input block allows you to select and connect specific digital lines or channels to your Simulink® model. After you have added a Digital Input block to your model, you can enter the parameters for its I/O driver. The following procedure uses the HUMUSOFT® AD512 I/O board as an example.


Sample time

Enter a value representing how frequently you want the block to execute and interact with the I/O hardware. The block will also synchronize your model with the real-time clock at this sample rate.

    Tip   If you are using a fixed-step solver, you must enter the value you entered in the Fixed step size box from the Configuration Parameters dialog box, or an integer multiple of that value.

Maximum missed ticks

Enter the number of timer ticks that your model can lag behind the real-time kernel. When the model lags by more than this number, the block reports an error and simulation stops. Otherwise, simulation continues even if some ticks are missed.

Show "Missed Ticks" port

Select this check box to display the current number of missed ticks as a block output.

Yield CPU when waiting

Select this check box to grant other programs more CPU time while the kernel waits for a response from the hardware.

Input channels

Enter a channel vector that selects the digital input channels you are using on this board. The vector can be any valid MATLAB® vector form. For example, to select the eight digital input channels on the AD512 board, enter

[1,2,3,4,5,6,7,8] or [1:8]

If you want to use the first four digital input lines, enter


If you have one 8-bit digital channel, enter [1]. If you have two 8-bit digital channels, enter [1 9], and from the Channel mode list, choose Byte.

Channel mode

From the list, choose one of the following options:

  • Bit — Returns a value of 0 or 1.

  • Byte — Groups eight digital lines into one digital channel and returns a value of 0 to 255.

Output data type

Set to specify the type of data that the block will output to the model.

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