Wayne and Layne

Picosecond imaging circuit analysis

Picosecond imaging circuit analysis (PICA) is a very cool method for measuring the activity of transistors in a CMOS integrated circuit. See [1] for details, but the basic idea is this: When a CMOS transistor switches state, it has a small probability of emitting an infrared (IR) photon. Since silicon is transparent to light with a wavelength longer than 1 micron, the IR photons can pass right through the silicon base of the chip. Researchers at IBM and elsewhere are setting up high-speed IR photodetectors to record these photons over many clock cycles, and produce very cool, visual records of which transistors are firing, and when in the clock cycle they are firing. As noted before, generation of an IR photon is not guaranteed, so the following movie was created from the records of a large number of clock cycles.

In this movie, the chip being tested has a distributed and hierarchical clock distribution network. This means that the initial clock buffered and amplified by a tree of buffers. As you can see in the video linked below, there is an initial pair of flashes near the top, followed by a large flash near the center, then a handful of distributed flashes, after which the chip lights up as all of the individual gates switch. Very cool stuff.

Here is a screenshot from the original source video at [2]:

1. Picosecond Imaging Circuit Analysis, J. C. Tsang, J. A. Kash, and D. P. Vallett, IBM Research
2. PICA Video, IBM Research

Ferroelectric RAM

Ferroelectric RAM (FeRAM or FRAM) is a type of non-volatile computer memory. It is similar in construction to DRAM, which is currently used in the majority of a computers main memory, but uses a ferroelectric layer to achieve non-volatility. Although the market for non-volatile memory is currently dominated by Flash RAM, FeRAM offers a number of advantages, notably lower power usage, faster write speed and a much greater maximum number (exceeding 10^16 for 3.3 V devices) of write-erase cycles.

Ferroelectric RAM

SensorLand: How do sensors work?

A bunch of cool pages about how different sensors work. Lots of cool illustrations.

sensorland – how do sensors and systems work

Antifuse – Wikipedia, the free encyclopedia

An antifuse is an electrical device that performs the opposite function to a fuse. Whereas a fuse starts with a low resistance and is designed to permanently break an electrically conductive path typically when the current through the path exceeds a specified limit, an antifuse starts with a high resistance and is designed to permanently create an electrically conductive path typically when the voltage across the antifuse exceeds a certain level.

Antifuses are also seen in the mini-light (or miniature) style low-voltage Christmas tree lights. Ordinarily (for operation from mains voltages), the lamps are wired in series. (The larger, traditional, C7 and C9 style lights are wired in parallel and are rated to operate directly at mains voltage.) Because the series string would be rendered inoperable by a single lamp failing, each bulb has an antifuse installed within it. When the bulb blows, the entire mains voltage is applied across the single blown lamp. This rapidly causes the antifuse to short out the blown bulb, allowing the series circuit to resume functioning, albeit with a larger proportion of the mains voltage now applied to each of the remaining lamps. The antifuse is made using wire with a high resistance coating and this wire is coiled over the two vertical filament support wires inside the bulb. The insulation of the antifuse wire withstands the ordinary low voltage imposed across a functioning lamp but rapidly breaks down under the full mains voltage, giving the antifuse action. Occasionally, the insulation fails to break down on its own, but “tapping” the blown lamp will usually finish the job. Often a special bulb with no antifuse and often a slightly different rating (so it blows first as the voltage gets too high) known as a “fuse bulb” is incorporated into the string of lights to protect against the possibility of severe overcurrent if too many bulbs fail.

Antifuse – Wikipedia, the free encyclopedia

Plug: LED Bargraph

Abstract: This project is a precursor to my forthcoming accelerometer project. I wanted to be able to visualize an analog signal using LED bargraph displays. In this project I explore capturing and smoothing an analog input signal, pseudo-multiplexing of output, and using a transistor as a switch to switch more current than the microcontroller can handle.

General Description: The device I am using for this project, the PIC18F452, has an integrated Analog to Digital (ADC) converter. This allows the microcontroller to measure an analog signal between 0 and 5 volts, and convert it to a 10-bit binary number. I am using a variable resistor, also known as a potentiometer, to easily create an analog voltage at pin 1 (AN0). In my program, I measure this value 128 times in a row, and then calculate the average of these 128 samples. The average voltage is scaled to be an integer between -10 and 10, inclusive on both ends. An appropriate number of LED segments are lit to represent the value.

LED Bargraph

Covox Speech Thing – Wikipedia, the free encyclopedia

Covox Speech Thing – Wikipedia, the free encyclopedia

Diebold Electronic Voting Machine – Owned

We watched this video in my Intro. to Operating Systems class today. Pretty scary stuff.