Oscilloscope Trigger

Overview

The Oscilloscope trigger is a function that can generate a pulse to an external test device when specific events happen. This feature is useful for monitoring bus events that occur intermittently. This is especially important in 10 BaseT1s because the Beacon is periodically transmitted - this makes it difficult to use a scopes traditional triggering mechanisms.

Figure 1 - The Oscilloscope Trigger is a falling edge trigger when an event happens.

Trigger Connection

On RAD-Meteor hardware you can connect to the trigger by attaching a wire to the trigger A signal as shown below. The trigger voltage is a 3.3V output that will go low when the trigger appears. It will automatically rearm after 5 microseconds or less.

Figure 2 - The blue wire shown connects to the trigger pin GP20.

Trigger Options

The RAD-Meteor currently supports the following triggers listed below. The Trigger is configured on the setup screens.

Trigger	Description	Notes
CRC Error	received message had an invalid CRC	occurs after message received in total
Logic Collision	A transmit was attempted but blocked by the PLCA	occurs after COL on MII occurs
Any Rx	Any received message	occurs after message received in total
Any Tx	Any successfully transmitted message	occurs after the message is successfully transmitted
Bus Collision	Physical bus collision - TxCol status bit	happens when TxCol status bit is set
Runt Frame	A runt frame was received	A runt frame is a frame under 64 bytes