Please excuse my electronics ignorance. I would like to be able to monitor the SCL clock line on a 24cXX I2C eeprom, so that I can watch for when the eeprom is 'read' by its host unit. Would any oscilloscope be suitable for this? I am seeing 'digital' and 'analog logic' on eBay. The clock line on these eeproms is only 100Khz or perhaps 400Khz. Picoscope looks nice.. but too expensive for this.
thanks for any help
Carl
Hi,
My $0.02 -
The problem with using a scope to do that is how are you going to relate the 'RD' signal to what is going on elsewhere? You really need to see some sort of timing diagram (or to trigger on the occurrence of a unique digital word) and the way to get that is with a logic analyser. If you should go for one of these on eBay, make sure it comes with the pods as they are often missing and as such the vendor cannot have tested it.
Having said all that, a scope would be nice as well for generally poking about. Nth-hand Tektronix scopes such as the 465, which won't break the bank, are favourite although there are plenty of others. There are also surplus Tek 7000 series mainframes around that take logic analyser plug-ins.
Cheers - Joe
Sounds like you need a logic analyzer more than a scope...
Well, I don't want to actually know anything, other than that the chip has just had its contents read... Just so I can get an idea firstly, that I'm looking at the correct eeprom, and more importantly, so I can figure out if there is a time-window within which I need to operate in order to in-circuit read the chip's contents. I'm using a very basic i2c to parallel-port adapter (a "non-driven" adapter using just 2x diodes and 2x resistors) with some neat Russian software to do the reading. It's working fine on what I suspected to be the correct eeprom, but there's another identical chip which is not responding.
Hi,
In that case, once the system has settled down, all you would need is a logic probe with memory. The LED would then come on if the read line was activated and stay on. Of course, you would have to have the polarity set correctly but you can get that from the EPROM data sheet. You could make for one a dollar.
BUFFER -> LATCH -> LED
The schematic for the HP probe and pulser are probably out there on the web.
Best of luck - Joe
Hi, I used my digital storage scope (tektronix) for this. A whole message can be stored by this. And later you can expand it (10x) and analyze it on a computer.
You can also use a logic analyzer.
Pieter
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