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Deep-memory oscilloscope platforms probe automotive FlexRay

Posted: 17 Mar 2006 ?? ?Print Version ?Bookmark and Share

Keywords:FlexRay? DL7400? DL7440? DL7480? oscilloscope?

DL7480 oscilloscope

As the FlexRay protocol accelerates, it will likely supplant predecessor controller area network (CAN) busing.

Not mentioned in Yokogawa Electric Corp.'s press statement is that its FlexRay signal analyzer oscilloscopes are available in two versions. There are 4-channel and 8-channel analog-input models. These instruments, with their nifty built-in printers, also play with host PCs running Windows.

Both boxes pretty much house everything you might need to analyze multiple mixed signals on a bus. Basically, these instruments work as 500MHz deep-memory scopes, but they're outfitted with analysis packages that meet the FlexRay v2.1 spec. However, as general-purpose scopes, they can also be used for other serial protocol analysis tasks, such as probing I2C lines, for example.

The basic scope hardware gives you a maximum sampling rate of 2GSps, with differential signal inputs using a differential probe. They can accommodate bit rates up to 10Mbits.

PHY analysis
With that, you can do PHY waveform and protocol analysis of FlexRay bus signals to look for things such as voltage levels, noise, and bus errors. As mixed-signal analyzers, DL7400 series boxes let you simultaneously measure up to eight analog signalswithout needing to sync separate oscilloscopes. Optionally, each model can include 16bit logic inputs.

The company's DL7440 model gives you four analog channels and a 16bit logic input. The DL7480 version gives you eight analog channels and the 16bit logic input.

The DL7440 scope's base price is under $14,000. Add about $4,300 to that for the FlexRay option, for a total that's just a bit over $18,000. For its part, DL7480 is priced at about $22,700. Again, add $4,300 for the FlexRay analysis package.

Deep memories
Both deep memory analyzers can also pack as much as 16-Mwords of recording memories, but base-price units are shipped with 4-Mwords. The 4-channel DL7440, equipped with 16-Mwords costs about $18,700. A 16-Mword 8-channel DL7480 will set you back about $28,700. Of course, you must add $4,300 for FlexRay.

Yokogawa also has a so-called Quick Zoom feature on these instruments. While some general-purpose scopes with high sampling rates may not be able to accurately capture waveforms if their memory depth is insufficient, the DL7400 series memory is big enough to support increased monitoring time.

Quick Zoom also lets you maintain a high sampling-rate to ensure accurate waveform representation. The Quick Zoom function can then be used to enlarge images on one or two segments of a waveform captured in the large memory.

Fast screen updates
These scopes also include what Yokogawa calls its All-Points Display. Due to their large memory arrays, the amount of information appearing on the scope's display itself can vary. This depends on whether you choose to display all points in a captured waveform, or just major values, such as maximum and minimums, in a given waveform segment.

In their All-Points mode, these scopes provide fast screen updating, so you won't miss elusive signals or have slow responses to instrument controls. In use, you can capture a FlexRay bus signal by specifying combinations of trigger bit conditions of Frame Start, Payload Preamble, Null Frame, Sync Frame and Startup Frame indicators.

You can also trigger on Frame cyclical redundancy check (IDCRC) errors on the FlexRay bus.

After capture, waveforms can be displayed with a list of analyzed frames. Frame waveforms can also be zoomed. With the scope's 8-Mword memory, continuous bus waveforms of up to 80ms can be captured at a sampling rate of 100MSps.

Observe while analyzing
This system works in real time, too. Since the frame waveform at a cursor in the generated list is automatically displayed, bus signals can be observed while analysis results are viewed. The effect of noise and level fluctuations on communication data, for example, can be determined during debugging. Results can also be saved to a text file.

The system's display mode also lets you analyze results on a frame-by-frame basis. Using that, you can show the time from a trigger point, each indicator bit, the Frame ID, payload length, data, CRC, and cycle-count, all in relationship to the captured waveform.

A desired frame or segment can also be located from within your captured data by searching. In a search you can use a Frame ID, cycle-count, a sync frame, or a CRC error (with AND logic). When frames are found that match your search conditions, signal waveforms are zoom-displayed.

Dual cursors
Bit width can also be displayed, according to the bit-rate. You do that with a pair of cursors. Values can then be checked while the cursor is moved by one or several bits at a time.

This kind of capability lets you observe long periods of bus data over multiple cycles so that you can confirm any changes or aberrations in timing and period. The triggers let you see whether a FlexRay chip, for example, is working properly, or whether the associated interface is at a fault. You can readily see whether sync frames were sent, and you can check for glitches.

USB reigns
The DL7400 series can be controlled using a USB-connected mouse. File names can be entered using a USB keyboard, and you can connect a USB printer for color print-outs. You can also connect USB flash memory for saving your acquired data, as well as instrument set-ups and screen images.

You can also use a PC program to remotely control a DL7400 series scope, again using USB. This is similar to control via IEEE-488/general-purpose interface bus.

Speaking of host PCs, using an Ethernet connection, you can perform various functions under Internet Explorer. You can copy and paste files from a DL7400's internal storage devices to your PC, or to a network drive. You can also perform actions such as waveform monitoring, uploading of settings, and starting and stopping measurements.

Using Windows XP's WebDAV function, a DL7400's internal storage media (a floppy, a ZIP drive, or a PC card) can be mounted as the network drive. Using your PC, you can then access stored data on these drives just as you would access data on the PC's own hard drive. This feature doesn't require any external FTP (file transfer protocol) software.

Your host PC can also automatically open an Excel spreadsheet, then periodically download waveform parameter values and graph them. Naturally, as a Windows function, you can also print a screen image on a network printer in the same way as you'd print to a USB printer. Finally, these instruments will let you transmit e-mail messages.

- Alex Mendelsohn

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