Tektronix 4000 Series, User Manual

Page: 157 / 326

Trigger Setup
10. If you are setting up an RS-232 trigger and
have made a
Trigger On selection of Tx Data
or Rx Data , push the lower-bezel Data button.
Push the Number of Bytes button and enter
the number of bytes with multipurpose knob a .
Push the side-bezel Data button, and enter
the parameters of interest with multipurpose
knobs
a and b .
I
2
C, SPI, and CAN Bus Trigger Data Matching
Rolling window byte matching for I
2
C and SPI. To use a rolling window to trigger on data, you de fi ne the number of bytes to
match. Then the oscilloscope uses a rolling window to fi nd any match within a packet, with the window rolling one byte at a time.
For example, if the number of bytes is one, the oscilloscope will attempt to match the fi rst byte, second byte, third, and so
on within the packet.
If the number of bytes is two, the oscilloscope will try to match any two consecutive bytes, such as one and two, two and three,
three and four, and so on. If the oscilloscope
fi nds a match, it will trigger.
Speci fi c byte matching (non-rolling window matching for a speci fi c position in the packet) for I
2
C, SPI, and
CAN. You can trigger on a speci fi c byte for I
2
C, SPI, and CAN in several ways:
For I
2
C and SPI, enter the number of bytes to match the number of bytes in the signal. Then use don’t cares (X) to mask the
bytes that you are not interested in.
Tektronix 4000 Series Oscilloscopes User Manual 139