Teledyne LeCroy Inspector - Users Manual - Manual (Page 9)

CATC CATC Inspector User’s Manual Version 2.31
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2.3.3 External Triggers
The CATC Inspector box offers two ways to generate an external trigger to control a recording
session: the “Manual Trigger” push-button, and the “EXT TRG” pin on the External Interface
Breakout Board.
2.3.3.1 The Manual Trigger Push-Button
The simplest way to generate an external trigger (when enabled in the Recording Options dialog
box) is by manually activating the Manual Trigger push button located on the front panel of the
Inspector box.
2.3.3.2 EXT TRG Signal Generation
In order to view a particular USB event (to determine—for example—how a particular device
behaves during the initialization phase), it is necessary to activate the CATC Inspector analyzer
to record the bus activities during a specific time period. If the USB host allows manual control
of the bus traffic, then in theory the CATC Inspector recording could be started manually at the
same time. Because of USB speed, correspondingly slow human reaction time, and buffer
memory limitations (1 Mbytes), however, manually coordinating the host actions with the
Inspector recording is generally impractical.
A simple solution is to generate a signal in the USB host PC, or in the USB hub or device under
observation, that will be synchronized to the particular event to be recorded. Such a signal can be
generated on the PC by calling a small software routine (see sample code below) that uses a
standard I/O Write command to a specific pin on an available serial or parallel port.
Alternatively, the EXT TRG signal might be generated by programming one of the general I/O
ports on the USB controller in the hub or device.
A short cable connects this (active low) signal to the EXT TRG pin of the External Interface
Breakout Board.
TRIG Signal Sample software Routine
case IOCTL_START_TRIGGER_RTS:
switch (gTriggerDongle) {
case SERIAL_PORT_TRIGGER_DONGLE:
outp (0x3fc, 00);
break;
case PARALLEL_PORT_TRIGGER_DONGLE:
outp (0x378, 00);
break;
}//switch
break;