Set input pin of chip under test to logic lowĬlock pin will be toggled from 0 to 1 to 0 during the test caseĮxpect logic low output from chip under testĮxpect logic high output from chip under testĮxpect high impedance output from chip under testĭont care - pin gets set with a weak pull downĮxploring the function of the device - reads the signal at the pin by applying a pullup/down check to confirm it's state as one of 1/0/Z Set input pin of chip under test to logic high GND of chip under test (set gpioL to low set gpioH to low) VCC of chip under test (set gpioL to high set gpioH to high) The python script " convertTxtDatabaseToC.py" performs the import and conversion. In fact this device can import tests that have been defined for Smart IC Tester because the syntax here is a strict superset. This test pattern syntax used here is based on that used by Smart IC Tester but is extended to include various new features including Z testing as well as codes that relate to exploratory testing that are unique to this device. The '/' character is a separator character that can be used anywhere in the test case and is ignored by the test framwork. Where the pin is an input then the codes define whether the signal applied should be a 1 or 0, and where the pin is an output then the codes specify what the expectations are of the pin's value for example whether the pin ought to be asserting a logic 1 or 0 output or whether it ought to be high impedance.Įxample: The test case "111G/HHZV" specifies the values and expectations of the pins from pin 1 to pin 8 in order, where pins 1-3 all as inputs set to logic 1, pin 4 will be the GND pin, we expect pins 5,6 to be outputs with logic high, pin 7 an outut in the high-impedance state, and pin 8 is Vcc. Usage Step1: Understand the test case specificationĪ test case is specified as a sequence of codes, one per pin, specifying whether the pin is an input or output of the test chip.
Note that the LED must be able to tolerate the forward current resulting from the inline two 150R resistors (approx 15mA). This device can also be used to test drive a pattern on an LED array or 7 segment display, with visual inspection to check the device's behaviour is correct.
Circuit coder tri state series#
This device is intended to test 74** series chips but will work equally well with 4000 series CMOS or other 5v chips that don't need much supply current. However, the device can operate in identification mode if needed. This device was not intended to be used to identify IC's as I can read that off the top of the chip. Nostalgia - I built something with a similar function at university in 1984 but it was a much bigger physically and hooked up to a BBC PC.To have some fun getting a PCB made up (not having to etch it myself like the old days).To allow me to check my understanding of the functioning of certain interesting and rarely mentioned logic chips.To test a bunch of chips I bought from eBay and AliExpress.There were various motivations for building this: able to differentiate equivalent logic devices that differ only in terms output type open collector outputs vs regular push-pull outputs eg 7405 vs 7404.verifies correct functioning of tristate outputs.interactive mode for device exploration.Hardware design and PCB can be found on EasyEda :
Circuit coder tri state software#
This software accompanies a hardware design for an integrated circuit test and exploratory tool.
Integrated Circuit Tester & Exploratory Tool
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