Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: krich on January 13, 2008, 10:46:29 PM
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Not exactly robot related, but here's my situation:
I've got an unknown IC with an array of 8 input pins (suspect its an IDS1100 or 1200 series, pins A0-A7). Two of them have built in pull-up resistors, the rest have built in pull-down resistors. The problem is that this is not the DIP form, its the die form. I can get to the pins (barely), but I don't know which pins are which. I just need to separate those that are high from those that are low.
Looking at the schematic on the datasheet, I'm thinking that I can test this with a continuity test to either the Vcc or GND rails without powering on the chip. Is this true?
If I need to power the chip to test it, what's the safest way to test? I don't want to inadvertently smoke the chip. Are these the results I should be looking for?
Voltmeter readings, testing from the pin in question to:
Test to GND, get 0v, this is a Low pin
Test to GND, get Vcc, this is a High pin
Test to Vcc, get 0v, this is a High pin
Test to Vcc, get Vcc, this is Low pin
This is probably pretty basic, but I'm still green at this and I only have one of these chips and I can't replace it.
Thanks for your insight.
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Looking at the schematic on the datasheet, I'm thinking that I can test this with a continuity test to either the Vcc or GND rails without powering on the chip. Is this true?
Get a multimeter with a continuity setting (it beeps if the circuit is true) - generally has the picture of a musical note plus a picture that looks like the symbol for a diode.
Select continuity mode on your meter and touch the probes togethr, you should hear a beeping sound.
Touch 1 to gnd on your IC and test the pins with the other, if you hear the beep then the pin has a pull down resistor.
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You can also do this with the ohm meter (resistance checker) that is a standard part of multimeters, set it to around 20K and touch 1 probe to gnd and test the other pins with the other probe if the screen shows a resistance value it is likely that the pin has a pull down resistor
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Thanks Paul. I guess I needed moral support more than anything. Turns out that the IC is a IDS1200, no internal resistors at all. Additionally, all 8 pins were tied together and then to ground (all this happening very near or under the die, I think). Short version of the story, I've figured out that there's no way I can get to the addressing features of that chip with how they have it set up. I destroyed the die trying to separate the pins. :-\
It was one of those voice recorder picture frames with a message from my daughter when she was 5. The record button inadvertently got pressed this afternoon, just for a split second. After doing research, I found that the device is like a cassette tape. The recording is still on the chip if its not been recorded over. If they had used a DIP rather than a die, I know I could have saved it. :'(
Such is life in the digital age. On the bright side, she's only 10, so I had better go find another frame and get her to record another message before she gets any older. Also, I've learned quite a bit about these Single Chip Voice Record/Playback Devices. I'm just going to have to think of a way to integrate that into my projects. ;D
Cheers,
Ken.