Frequently Asked Questions - FS2220, FS2221 & FS2229 AGP Analysis Probe

Here are some answers on some of the more common questions we receive regarding our AGP Analysis probes.

Q. What is the difference between your three AGP analysis probes, the FS2220, the FS2221, and the FS2229?

A. The FS2220 is for timing analysis only. It supports AGP speeds of 66 MHz (1X) and 133 MHZ (2X). The FS2221 is for state analysis only. It supports AGP speeds of 133 MHz (2X) and 266 MHz (4X). The FS2229 is for state analysis only. It supports AGP speeds of 533 MHz (8X).

Q. Why is the FS2221 only supported on the Agilent 16715A, 16716A and 16717A cards. Why do I have to use an Agilent 16700A or 16702A?

A.The Agilent 16715A, 16716A and 16717A cards are the only Agilent logic analyzer cards that have a minimum clock pulse width spec that will meet the requirements of the AGP4X. Also, the setup and hold time requirements of AGP4X are only met with these cards. The Agilent 16700A and 16702A are the only Logic Analysis System mainframes that support these cards.

Q. Why can't I use the Agilent 16717A card? It has a maximum state speed of 333 MHz, which is more than the 4X speed of 266 MHz.

A. Good question. If you will read the Agilent specifications for the 16717A, you will notice that at the 333 MHz speed, the 16717A reverts to what Agilent calls "Supplemental Specifications and Characteristics". This allows only one clock and one machine. The FS2221 requires three clocks and two machines, so we can't use the 16717A in the 333 MHz mode. We demux the 266 MHz speed down to 133 MHz, well within the bandwidth of the Agilent 16715A, 16716A and 16717A cards, and also can use three clocks and two machines in our measurement.

Q.How do I find out what are the latest versions of Agilent logic analyzer operating software?

A. Contact your nearest Agilent Call Center.

NOTE: We have been advised by Agilent that for proper performance of our FS2221 AGP4X Analysis Probe, it will be necessary for you to obtain two "patches" from them for your Agilent 16700A/702A operating system. To obtain the patches, call the Agilent Call Center at 800 452-4844 and ask for patches 034 and 035 for version 1.4 of the Agilent 16700A/702A operating system.

Q. How can I get the FS2221 to work with 2X speeds?

A. The FS2221 requires the motherboard to supply the reference voltage to the AGP probe in all cases. This voltage must be at pin B66 of the AGP connector. An AGP 2X motherboard probably does not do this and therefore is not suitable without some rework. It may be possible for the user to add a wire to the motherboard AGP connector. Then they need to remove the key in the motherboard AGP 2X connector. In no case should the user modify the probe of the FS2221.

Q. When plugging in the AGP 4X interposer board it is unclear as to which side of the graphics card should be connected to the interposer. Is it side A or B?

A. The Component side of the graphics card should be connected to Side B. We are also going to start adding stickers to the interposer board to make it clearer. We now have a note on the interposer board which points to which end of the interposer board the front panel of the graphics card should be. We felt this was clearer than saying Component Side. We have seen cards with components on both sides!

Q. Page 12 of the user manual talks about calibrating the FS2221. Can you explain what is the purpose of doing the calibration? If for any reason the calibration fails, is there a feedback mechanism in place to tell the user about the pass/fail (possibly an LED flashing or some type of a message)?

A. The cailbration is to de-skew the clock to the data. The switch activates an A/D converter which sends a signal to a programable delay. The delay value is then loaded. The value is factory set but it needs to get re-loaded each time the unit is powered up. We have added this to the manual.

Q. How do I qualify the probe in the target environment?

A. We suggest that you run repeatable data pattern transfers at 2X and 4X and then use the Logic Analyzer compare tool to verify that the data is captured by the probe correctly. We do not provide details on how you are to make your platform and graphics card do the repeatable data patterns. You should be able to write the code to do this simple type of test.

Q. I want to verify that the FS2221 AGP4x probe only interfaces with 1.5V AGP video cards. If this is true, do you have an 3.3V interposer available?

A. The FS2221 is capable of capturing 3.3V signaling transactions on the AGP 4X bus with limitations. The motherboard must have a AGP Universal connector and it must provide a Vref to the adapter. We will work in a motherboard that has a new chip set like Camino because it provides a Vref all the time regardless of whether it is in 2X or 4X mode. An older AGP 2X MB does not provide a Vref to the AGP connector and will not work with our probe.

Presently, our interposer uses an AGP connector that has a key for either 2X or 4X. We position the connector so that the key is in the 4X position. As a result, the adapter card must also have a cutout in the 4X location for it to insert into the connector. In the near future, we hope to have an Universal connector placed on the interposer so that there will not be any adapter card restrictions regarding 1.5V or 3.3V.

Q. We want to measure the exact timing data from our AGP4X chip. The FS2220 can support timing measurements up to 2X mode, but our chip is running at 4X speeds. The FS2221 is designed for state analysis only. Do you have any suggestions for 4X timing measurements? We'd rather not touch the probe & cable, because it will affect the load impedance. But the timing measurement is necessary for us.

A. When we were developing the FS2221 analysis probe we needed to make timing measurements from the target to ensure that the probe was capturing the data correctly. The only way to do this was using a scope with an active probe. We used the Agilent Infinium scope, which has a 8 GHz bandwidth. We found this to be sufficient. Now the problem arises that you can only see a few signals at a time. So, we always had to probe the strobe and then we looked at a data signal to see how it looked. The problem here is that you need to have both strobes (differential) and then the data signal. So if you have a scope that can give you 8 GHz on 3 or more channels that would be best (the Infinium only gave us 2). We used the scope in conjunction with the logic analyzer. For example, since the logic analyzer could see all the signals at once, we could use that to provide the trigger (on a failing pattern) then the logic analyzer triggered the scope. We would then use the strobe transitions to count and line up the exact time of error with the logic analyzer. With this technique we could see the failing bit with a scope at the exact right time.This technique is tedious but we found no other accurate method.

Q. 1. The front panel of the FS2221 has a switch to change between 1.5V and 3.3 V. In the format configuration window, the level is adjusted to 1.1V. As far as we have found with AGP 4X, you have to use 1.5V. Are AGP 1x and AGP 2x for 3.3V?

A. Per the AGP spec, 2X operation can be at 1.5v or 3.3v. 4X operation is at 1.5v. This is the signaling level on the bus. The voltage that we have set in the FORMAT menu is what the box is signaling the logic analyzer at. This level has nothing to do with the voltage level present on the bus. If you wish to get more background on the AGP bus itself may I suggest you go to the AGP Implementors Web site at http://www.agpforum.org.

Q. When do we have to use 1.5V and when do we have to use 3.3V? Is it possible to run into any conflict, because you have to have 1.5V and 3.3V?

A. If your target is running at 4X it will be most certainly 1.5V. If it is 2X it is PROBABLY 3.3V but it could be 1.5V. You will need to check the spec's of the target. The only conflict you might run into is if you have the switch set to the wrong position for the target signaling level. You will not harm the target or the box if this is the case. However you will not acquire the data properly if the switch is in the wrong position. Again, you need to know the spec's of the target you are running in.

Q. How can you tell in the "Listing Window" whether it is a AGP4x signal or a AGP2x signal?

A. From a protocol point of view the AGP2X signals are the same as the AGP4X signals...the only difference is the speed. The Inverse Assembler cannot read the time stamp so it cannot tell. But if you see the time difference of 12-16ns between AGP data transfers, that indicates 2X transfer speed. If the difference is 4-8 ns, then you are at 4X speeds. Targets cannot switch between 2X and 4X on the fly.

Q. How do I know which Agilent logic analyzer is best for my needs?

A. Click here

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