Input Configuration

For GPI configuration, you have two signal modes available: Mode "Single-ended", and mode “Differential”. Mode "Single-ended" is the default mode.

To use the input pin pairs B1/B2 and A1/A2 on the GPIO socket for receiving differential signals, you have to switch them to “Differential” mode.

 

Switching to "Differential" Mode

 

The physical interface of the GPIO is configurable. If you need another configuration of the input signals, i.e.:

  • Pull-down mode,
  • 2 differential signals (and no ingle-ended signals),

you can easily configure the GPIs according to your needs. For configuration, you use a command line tool which has been installed on your system together with the Silicon Software runtime.

For more information, see Input Configuration and Configuring the Physical Properties of Trigger Signals.

   

 

 

You can switch between the modes "Differential" and "Single-ended" using the command line tool as described in Configuring the Physical Properties of Trigger Signals.

Single-Ended Mode (Default Mode)

In default configuration (“Single-ended” mode), all four input pins of the GPIO are configured to receive single-ended signals (in pull-up mode):

 
  • Pin A2
-> 1 single-ended signal
 
  • Pin A1
-> 1 single-ended signal
 
  • Pin B2
-> 1 single-ended signal
 
  • Pin B1
-> 1 single-ended signal

 

Differential Mode

If you need differential input signals, you can switch the GPIs of your Front GPIO into "Differential" mode. In "Differential" mode, fourinput pins of the GPIO are configured to receive 2 differential signals:

 
  • Pins A1/A2
-> 1 differential signal (pin A1 +, pin A2 -)
 
  • Pins B1/B2
-> 1 differential signal (pin B1 +, pin B2 - )

How to switch between "Single-ended" and "Differential" mode, see Configuring the Physical Properties of Trigger Signals.

 

Custom Configuration “Pull-Down”

 

Both configurations (Differential and Single-ended) can be used in pull-up and pull-down mode. Default is the pull-up mode. If you want to use the inputs in pull-down mode, you can configure the pins accordingly, see Configuring the Physical Properties of Trigger Signals.

   

Electrical Characteristics of the Physical Inputs:

Electrical

Minimum

Typical

Maximum

Unit

Supply voltage 4.5   28 V
Input threshold   20% Supply Voltage    
Differential voltage   10   mV

Timing Characteristics of the Physical Inputs:

Timing

Minimum

Typical

Maximum

Unit

Propagation delay 40 60 80 ns
Min. pulse width   200   ns
Max. frequency   2.5   MHz

 

 

Board Protection

 

LightBridge 2 VCL has been designed with a varistor which opens at an input voltage of 30V (on the GPIOs) to let the onboard surge protector get active to protect the board. At a total supply voltage of 36V, the electronic chips would become defective.