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Design Talk: February 2010

Wed, 01/20/2010 - 5:57am

Touchless, Holographic HMIs Prevent Disease Transfer

RDMPortraitBy R. Douglas McPheters, HoloTouch Inc., www.holotouch.com

The New York State Health Department’s June 30, 2009 Hospital-Acquired Infections Report has drawn serious attention of healthcare professionals and the public to the daunting challenges faced in eliminating contamination and disease transmission rampant in hospitals and other healthcare facilities. Unfortunately, this report and others spawned such Earth-shattering recommendations as the importance of washing hands while at work in healthcare facilities. While useful, that procedure was part of the syllabus for the health merit badge I earned on the way to becoming an Eagle Scout in the ‘50s. A much younger person might say “hello?”

We all have friends who’ve returned home from hospitals with serious infections contracted for reasons unrelated either to their reasons for seeking treatment in the first place or their medical procedures. My personal favorite is a now-deceased friend who entered a local hospital for implantation of a pacemaker and returned home with a staph infection in her foot. Regrettably, many laudable suggestions on ways to reduce the spread in healthcare facilities of diseases and infections, particularly in our virus and H1N1-laden world, however well-intended, can best be described as “feel good” measures akin to the ubiquitous anti-bacterial lotion dispensers we’ve all seen metastasizing in healthcare facilities and various public facilities. As I understand it, washing hands is important but useless unless pursued vigorously for at least 30 seconds. Sadly, many measures suggested as cheap or simple ways to reduce transmission of contamination and disease are destined to be unproductive because they either require overworked, distracted or disinterested people to do still one more thing or necessitate use of additional equipment or supplies that are not efficient, however well advertized.

Fortunately, touchless, holographic human-machine interfaces offer a simple solution that doesn’t require people to do more than they already do – they need only pass a finger through a holographic image, floating freely in the air, of what would otherwise be the keys or buttons of equipment to be operated. These HMIs for electronics and electro-mechanical equipment offer inexpensive and intuitive ways to bypass transmission of contamination, dirt and disease because there’s nothing to actually touch in using them. Touchless, holographic HMIs have only three essential and simple components: a full-color hologram of what would otherwise be keys or buttons of the equipment laminated on the back of an acrylic plate, an LED behind the acrylic plate that projects the hologram’s image into the air and a wave source sensor, usually infrared, also behind the acrylic plate, that is focused on the center of the freely floating holographic image. When a finger enters the holographic image, the sensor sends an actuation signal to the device. For example, take a look at the lowly, metal mushroom on the hospital wall that family, patients and staff elbow, hit, punch or shoulder to actuate the mechanism that opens exit doors. Not only is that device crawling with whatever was on the body, clothing or hands of all previous users (seldom if ever cleaned) but it must be regularly replaced due to heavy use and abuse. By contrast, touchless, holographic switches have no moving parts to fail under heavy use and only passing a finger through their colorful, holographic images, suspended in the air, is needed to open the doors. These components can be easily customized to a wide variety of electronic and electro-mechanical devices such as medical equipment, kiosks and doors, whether in primary hygiene sites such as operating rooms or less directly invasive venues such as healthcare facility corridors, examining rooms and public areas.

 

Leveraging Useful Skew

By Sunit Bansal, Sumeet Aggarwal, & Kapil Narula, Freescale Semiconductor, Inc., www.freescale.com 

Introduction
Useful skew is one of the most important steps to meet timing. But the scope of useful skew is limited in timing critical paths. Our idea tries to increase the scope of introducing useful skew in timing critical paths by exploiting non-timing critical paths.

What is Clock Skew?
Difference between the clock arrival times for the launch and capture flops is termed
as clock Skew. As shown in Fig. 1, the difference in clock latencies for flop2 and flop1 is
(7.2ns – 7.0ns = 200ps)

Figure1-Freescale-web

Question: How Clock Skew helps in meeting timing?
Answer: Useful Skew

Lets assume that the path from flop1 to flop2 is violating by 250ps. Following is the sequence of steps that can be done to meet the timing using useful skew.

1. Identify the slack value “to” the violating register (flop2 in Fig2)
2. Identify the slack value “from” the violating register (i.e. slack value from flop2 to flop3 as shown in fig2)
3. If slack value in step (2) is greater that slack value in step (1), the clock of violating register can be pushed such that the timing is met.
4. Check for further violating registers and gain on timing.

Figure 2-Freescale-web


The situation after pushing the clock is shown in Fig3.

We can notice that now the timing paths are meeting:
a. Timing slack “to” flop2 has changed to 0.050ns from -0.250ns
b. Timing slack “from” flop2 has changed to 0.450ns from 0.750ns

Figure3-Freescale-web

Useful Skew can be more useful
1. Let’s revisit Fig2 (shown here again). This time the slack “to” the violating register is shown as -0.950ns.
2. Now even after pushing the clock arrival for flop2 by 750ps, we would still not meet timing as shown in fig4. The path “to” the violating flop2 would still violate by 200ps (after inserting a RED clock buffer with 0.750ns delay)

Figure4a-Freescale-web

Figure4-Freescale-web

We can make useful skew more useful by following our 3-pronged strategy.
Let’s revisit Figure2
1. Increase the uncertainty “from” violating register so that the slack of 0.750ns is more pessimistic. Lets assume the new slack is -1.5ns. Also decrease the uncertainty “to” the violating register such that it is meeting timing. This is shown below

Figure5-Freescale-web

2. Do Optimization of the design after finding all such occurrences. Following figure shows the slack values after optimization.


Figure6-Freescale-web

 3. Remove the extra uncertainty after optimization. Now the slack would be 1.1ns. Now notice that before the strategy the slack was 0.75ns. Now it has changed to 1.1ns. Also, Slack to the violating register has changed back to -0.950ns.

Figure7-Freescale-web

Corollary:
Because of extra uncertainty, timing path “from” violating register would have more slack. Hence we would get sufficient scope to further push the clock at flop2. Now Figure4 would change as shown below. 

Figure8-Freescale-web

The idea could be further extended to more register levels. Essentially we can generate more useful skew margin through cascading registers. For e.g

Even after increasing the uncertainty, the path from the “violating register” (flop2) has a slack of 0.750ps.
1. Still there is no sufficient scope of pushing the clock at flop2. We still need to generate 200ps more.
2. Path from Flop3 to Flop4 is meeting by 0.050ns.
3. We can extend our idea to Flop4 and increase the slack from flop3 to flop4 as shown by the dialog box.
4. Now clock at flop3 can be pushed further by 200ps
Finally All the timing paths, namely
a. Flop1 -> Flop2
b. Flop2 -> Flop3
c. Flop3-> Flop4, would be meeting timing. 

Figure9-Freescale-web

Freescale-Flowchart-web

 

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