MCU微控制器技術
與應用論壇
Getting the most
from your
oscilloscopes
Why are we here today?
Discuss hidden features that can improve the usefulness of your
current oscilloscope
Learn tricks for implementing more advanced techniques in
basic scopes
Learn about tools that you can add to latest-generation scopes
to upgrade their performance.
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A quick caveat
These features and techniques are implemented on Agilent
oscilloscopes.
Many, but not all can be used with other manufacturer’s scopes.
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Topics
Triggering
Techniques
Mask/Waveform
Limit Testing
Going Beyond the
Bench
Low-Speed Serial
Analysis
Looking in Places
Normally Off-Limits
• Finding runt pulses
• Stabilizing bursts with trigger hold-off
• Three techniques for finding glitches
• Using AutoMask
• Importing an industry-standard mask
• Multiple test criteria
• What is LXI ?
• Troubleshooting in intercontinental teams
• Three tools for analyzing data on your PC
• Monitoring bus health
• Viewing and triggering on bus protocol
• Isolating errors with triggers and segmented memory
• Saving Channels with MSOs
• Viewing events inside your FPGA
• Deep analysis in the frequency domain
Triggering Techniques
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Finding runt pulses
No scope manufacturer owns the
IP − mostly used in higherpriced models.
Some runt events can be found
with a pulse-width trigger.
A runt trigger can be
implemented using a Duration
trigger (pattern + time qualifier)
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Runt trigger technique
•
•
•
•
•
Double probe the test point
Set trigger pattern for Ch1=0 and Ch2=1
Set trigger thresholds for Ch1 and Ch2 for runt limits
Increase qualifier time to eliminate transitions
Digital channels can be used to save analog channels
1
2
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Stabilizing bursts with trigger hold-off
Can a scope be too fast?
It is difficult to stabilize the
display of pulse bursts.
Edge triggers catch every edge
Pulse width triggers can isolate
pulses of a given width, but
require some thought to find
the optimal settings.
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Trigger holdoff technique
• Holdoff inserts a delay before the trigger circuit rearms
• Dial up holdoff value until edge trigger stabilizes
(usually widest pulse, or inter-burst dead time)
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Finding the glitches you know about
Isolate with a pulse-width trigger
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Finding glitches that you suspect
•Use infinite persistence to
spend more time browsing
without having to “babysit”
the scope
•Useful for scopes with slow
update rates
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Finding glitches that you don’t know about
Turn up waveform
intensity to maximize
variable persistence
Browse 5 seconds on
each pin
Requires a fast real-time
update rate
(RIS not acceptable)
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Mask/Waveform
Limit Testing
• Using AutoMask
• Importing an industry-standard mask
• Multiple test criteria
• Six Sigma mask testing
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Using AutoMask
• Accumulate valid pass/fail statistics , in this example
• 39 errors were detected among 1.06975M waveforms
• Error rate = 0.0036%
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Importing an industry-standard mask
• FlexRay eye-diagram mask test
• 8-bit multi-polygon mask was created on a PC using a text editor
• Import the mask and setup parameters through USB memory stick
• Set up the test criteria to “stop-on-error”
• In the following example , the 1st violation of the mask occurred after
testing more than 44000 waveforms (350,000 bits tested )
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Multiple test criteria
• Choose from multiple options
• Run forever (with accumulated pass/fail statistics)
• Run until a specified number of test
• Run until a specified time duration
• Run until a maximum ideal “sigma” standard
• Stop-on-failure
• Save-on-failure
• Print-on-failure
• Trigger out on-failure or on-pass
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Six Sigma mask testing
• Acquiring enough samples for 6 Sigma resolution
• Using InfiniiVision scopes takes only 3.3 seconds
• This figure shows a test of 1.26 million waveforms under 18
seconds that provides resolution to 6.3 sigma.
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Going beyond the bench
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What is LXI?
LXI = LAN eXtensions for Instrumentation
All major and minor T&M vendors are members of the
consortium
Succeeds GPIB
•Faster data transfer (up to 125x)
•LAN is native to all PCs (no special cards and cables)
LXI devices contain a web server
Programmatic interface (IVI-C, IVI-COM) to your language
Agilent scopes are LXI Class-C
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Troubleshooting in intercontinental teams
• Set scope up on the LAN in a remote lab or plant
• Multiple users can view and control the scope
• Some just want to save a trip to the lab from the office
Scope web page
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Remote display/control
Analyzing data on your PC − IntuiLink Data
Capture
Methodology:
1.Connect PC to scope using
LAN,USB or GPIB
2.Download images or data
directly to PC from scope
3.Process data with your
programs or with apps like
MATLAB®, MathCAD®
Free download from agilent.com
Note: LabVIEW® drivers are also available, but
do not use IntuiLink infrastructure
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Analyzing data on your PC − IntuiLink
Toolbars
Methodology:
Typically used for quick
documentation or analysis
•Small data records
•Measurement results
•Screen images
Works with Excel® and
Word®
Free download from
agilent.com
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Analyzing Data on your PC − Offline Viewer
Methodology:
Capture multiple deep memory traces
without tying up scope for analysis.
Use markers, zoom, search, charting,
listing to perform deep analysis.
Compare many traces captured at
different times, side-by-side
Multiple users can perform offline
analysis
B4610A is an optional toolset that can
work with any scope that can save
CSV or a defined BIN format.
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Low-Speed Serial Analysis
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Monitoring bus health
Serial busses are common in
embedded designs
Bus counters give you quick
insight into bus traffic and
errors
Counters do not require
triggers − easy to execute
Basic counters can be
implemented w/o a dedicated
bus toolset using SW tags and
digital channels
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Viewing and triggering on bus protocol
Traditional technique is a
manual decode/ strip chart
Decoding tools simplify this task greatly
− most newer scopes can be upgraded
Hardware triggers are used to isolate
events of interest, like this balky bit
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A Quick Note About
Hardware vs. Software Approaches
• Triggering and Decode are based on the same hardware
– This minimizes discrepancies that you may find with architectures that
use HW for triggering and SW for decode
• Update rate – Up to 100,000 waveforms/sec in the InfiniiVision architecture
– Important for viewing dynamic signal activity (switching signal that affects
decode)
– Important for viewing infrequent problems
• Error conditions that are caused by signal integrity issues
• Quickly characterize bus success/failure with counters
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Isolating errors with triggers and
segmented memory
Traditional Deep Memory
“Swallow and wallow”
Provides the ability to
capture a long record
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Memory is still used
during idle time
Segmented Memory
Efficient use of deep memory
• Don’t waste memory on idle
• Capture much more time
Segmented Memory Technique
• Use trigger to isolate
intermittently bad
packet
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Segmented Memory Technique
• Use trigger to isolate
intermittently bad
packet
• Step through segments
to compare good
packets …
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Segmented Memory Technique
• Use trigger to isolate
intermittently bad
packet
• Step through segments
to compare good
packets …
• … from bad
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Segmented Memory Technique
• Use trigger to isolate
intermittently bad
packet
• Step through segments
to compare good
packets …
• … from bad
• Use infinite persistence
to highlight the
differences
Alternate technique: Capture just the error events
to look for patterns in up to minutes of traffic
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Isolating Errors with Segmented Memory
• Acquire 500 frames with errors only
– Easily scroll through frames and look for anomalies/errors
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Flexible usability of analog and digital
channels of an MSOs
• Add 16 digital channels at a low price per channel
• Existing owners can perform the upgrade on their bench
• Serial analysis can be performed on either digital or analog channels
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Looking in Places Normally Off
Limits to a Scope
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FPGAs
Rapid Altera and Xilinx FPGA debug using on-chip MUX core.
1.Quickly access internal FPGA signals
2.Access new sets of internal signals in seconds using minimal pins without stopping
design or changing device timing.
3.Automated setup MSO
1. Signal & busing naming
2. Threshold level
Select
Capture
Mode
Resource
Estimate
ATC2 pin
location
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# of
debug
pins
# of signal
banks
Frequency Domain and Modulation Domain
• All modern scopes offer FFT
• Agilent VSA software works with all Agilent real time scopes (CSV data)
• Wideband spectrum analysis (to scope bandwidth)
• Noise reduction allows up to 12-bits of vertical resolution
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Adapting Your Scope
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Adapting your Scope – I2S
What is it?
• I2S – Inter IC Sound
– Serial protocol for two channel digital audio streams
– Used in CD/DVD players, MP3 players, TVs, etc
– 3-wire protocol
• SD (serial data) – MSB first
• SCK (serial clock) – continuous signal
• WS (word select) – Which channel (0 = Left, 1 = Right)
SD D1 D0 D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
SC
WS
Left Channel
Right Channel
Timing Diagram of 16 Bit Audio Example – Left and Right Channel
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Adapting your Scope – I2S
Relationship between SPI and I2S
• I2S is not currently a native capability in InfiniiVision scopes
– I2S is very similar to SPI 3-wire
SPI
I2S
Clock Line
CLK
SCK
Data Line
DATA
SD
CS
WS
Select Line
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Adapting your Scope – I2S
Relationship between SPI and I2S
I2S Equivalent
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Serial
Clock
Serial
Data
Word
Select
Adapting your Scope – I2S
Using SPI Triggering for I2S
• 16 bits (up to 32 bits)
– The first bit needs to be
a “don’t care”
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Adapting your Scope – I2S
Using SPI Triggering for I2S
• 16 bits (up to 32 bits)
– The first bit needs to be
a “don’t care”
– The second bit is the
MSB of the next data
frame
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Adapting your Scope – I2S
Using SPI Triggering for I2S
• Use the “Frame By”
button to denote left or
right channel
– ~CS = Left Channel
– CS = Right Channel
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Adapting your Scope – UART
• RS232 is a subset of UART
– Many LSS protocols are based on the flexibility of UARTs
• InfiniiVision oscilloscope support is designed to be flexible
– Settings for
• 5 to 9 bits (including 9th bit when needed for UART)
• Polarity
• Parity
• Baud rate
• Bit order
– Flexible triggering and decode
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Adapting your Scope – UART
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Adapting your Scope – UART
User definable
number of bits
from 5 - 9
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Adapting your Scope – UART
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Serial Bus Protocol Viewer
Only available in MSO/DSO9000A
4 new protocol analysis applications
• I2C/SPI
• RS232/UART
• PCIe
• USB
Protocol analysis is much powerful than
serial bus decoding
To make sure real time debugging
Serial bus protocol triggering is implemented
by hardware of MSO/DSO9000A
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