If you have something you think should be added, please E-mail Dr. Cady

"Dithering" of A-Ds either as a signal added to the reference or to the signal to be measured is an accepted technique. It works, but only under a tightly constrained set of input and sampling conditions. As well as white noise, a triangle wave can be used as the dithering signal, with the obvious limitations that its period should be an integral number of sampling intervals, the averaging period > should be one dither cycle in length and that the signal to be measured should not change during the averaging period.

If you want to convert at 100 MHZ these techniques are unlikely to be much use to you. At DC they may be worth looking at.

The Voltech PM1000 AC power analyzer uses this technique - open one up and you'll find a lowly 8-bit ADC inside. Their dither signal is a 600 Hz triangle wave, 1 ADC unit p-p. The approach they use is fairly well documented in the service manual for the product.

I have done a bit of experimentation with dither applied to DC signals. In this experiment, I used a 600 Hz triangle wave (same as Voltech), sampling the signal 256 times at a rate of 3840 Hz (60 Hz * 64). The final result was a 16-bit number (fully 16 bits if the input was at the Vrh level). A 16-bit DAC was used to furnish the test signal. Usable resolution increase was 3 to 4 bits, with the lower 4 bits mostly random.

A control case was also set up, using the exact same hardware and software but with the dither turned off. The results seen were consistent with what one would expect from a 8-bit AD; e.g. the low 8 bits of the 16-bit result were meaningless. Plotting scatter diagrams of both test runs (X=DAC input, Y=ADC result) was quite illustrative; the dithered signal plotted a smooth diagonal line, whereas the control run plotted the expected stairstep function. These experiments went a long way towards adding to my understanding of ADC technology, giving visual meaning to terms like "monoticity", "differential non-linearity", "accuracy" and such.

Amusing anecdote: The reason for performing these test runs was to satisfy an engineer on the project who was convinced that adding dither to a DC signal to increase resolution would not work. This guy actually believed that a spec like "+/- 3 LSB error" meant that ANY 3 bits of the ADC result could be in error - not just the low three bits, or a +/- 3-count potential error.

Thanks to: Mark Schultz <mschultz(aatt_sign)jps.net>

iButtons are very rugged, about the size of a stack of 4 quarters, and can be had with clock, memory, ID#, etc. They are extremely rugged (stainless steel can) and are being used for building security, hotel door access, US Postal service letter carrier delivery logging, etc. There are only 2 contacts and a variety of rugged, compact connectors are available. IButtons cost a lot less then parallel port dongles. In fact, some dongles have the iButton chip inside them.

http://www.ibutton.com
Thanks to: Bruce Boyes <bboyes(aatt_sign)systronix.com>

App Note 74 Reading and Writing iButtons via Serial Interfaces http://www.dalsemi.com/DocControl/PDFs/appindex.html

ftp://ftp.cmf.nrl.navy.mil/pub/kenh/minilib.tar.gz

Code to talk the Dallas One-Wire protocol is included. Also included is sample C code that implements the bus discovery protocol.

It's actually pretty easy to do the protocol. The timing requirements are fairly lax; you have to add some NOPs even with a 2MHz HC11 to get the right delay. The data sheets include the complete protocol.

Ken Hornstein

http://www.hantronix.com
http://www.repairfaq.org/filipg/LINK/F_LCD_menu.html
LCD Frequently Asked Questions
ftp://ftp.ee.ualberta.ca/pub/cookbook/faq/lcd.doc
http://www.eio.com/lcdintro.htm
http://www.senet.com.au/~cpeacock/serial3.htmInterface a LCD to a RS232 line
Sites discussing interfacing:
http://www.iaehv.nl/users/pouweha/lcd_examp.htm
http://www.eio.com/lcdintro.htm
http://www.senet.com.au/~cpeacock/serial3.htm

Motorola's XMMAS40G10x comes in a 16 pin dip package, is a micromachined accelerometer reading +/-40G linear, with .1G resolution if I remember right. Output is a voltage, the device requires +5V.

Check out the Analog Devices ADXL05, a great single chip solution with a minimum external part count. Info is available at the analog web site http://www.analog.com

 
********************************************************************
*   Infra Red Decoding for Soy, Mitsubishi and JVC                 *
*   1/1/90                                                         *
********************************************************************
*   The SONY IR packet consists of three repeated words with       *
*   encoding done as variable width bursts of 40khz IR.            *
*   Inter word gap is 26.0ms                                       *
*   Start bit is       2.5ms                                       *
*   One bit is         1.3ms                                       *
*   Zero bit is        0.7ms                                       *
*   Inter bit gap is   0.7ms  (IR is OFF)                          *
*   12 bits per word                                               *
*   MSB First                                                      *
*                                                                  *
*                   1     0     1     0    0    ...                *
*   ___          _      _    _      _    _    _         __.._      *
*      |________| |____| |__| |____| |__| |__| |__...._|     |__   *
*        Start     Bit 1   2     3     4    5        12       Start*
*                                                                  *
********************************************************************
*                                                                  *
*   The NEC IR packet consists of a start sequence followed by 32  *
*   data bits encoded as variable width off pulses.  The first 8   *
*   bits are the ID (21) then repeated as complement.  Then comes  *
*   the 8 data bits followed by their complement.  after 40 ms     *
*   comes a repeat sequence.                                       *
*                                                                  *
*   Homeminder uses this encoding with ID = 21                     *
*   Kenwood CD Player                  ID = B6                     *
*                                                                  *
*   Start bit is       9.0ms of on                                 *
*   FIrst off bit      4.5ms of off                                *
*                                                                  *
*   One bit is         1.6ms of off                                *
*   Zero bit is        0.5ms of off                                *
*   Inter bit gap is   0.7ms of on                                 *
*   8 bits ID and 8 Bits data and their complement                 *
*   MSB FIRST                                                      *
*                                                                  *
*                     1    0    1    0    1     1                  *
*   ___         __   ___   _   ___   _   ___   ___       __.._     *
*      |_______|  |_|   |_| |_|   |_| |_|   |_|   |...._|     |__  *
*        Start     Bit 1   2    3    4    5     5        32   rpt  *
*********************************************************************
*   The MITSUBISHI IR packet consists of three words with encoding *
*   done as variable off periods separated by 500 us bursts        *
*   Inter word gap is 26.0ms                                       *
*   Start bit is       0.5ms                                       *
*   One bit is         2.0ms                                       *
*   Zero bit is        0.7ms                                       *
*   Inter bit gap is   0.5ms                                       *
*   MSB First, First bit is start bit                              *
*                              0     1     0    1       1          *
*   ___   ____   ____   ____   __   ____   __   ____   ____        *
*      |_|    |_|    |_|    |_|  |_|    |_|  |_|    |_|    |_|     *
*      Start               BIT  1    2     3     4      5          *
*                                                                  *
*                                                                  *
*   Ignore first bit then ID = EA then 8 bit code                  *
*                                                                  *
*            0 1110 1010 XXXX XX00 only 6 bits active              *
*          MSB                                                     *
*********************************************************************

One source of information is the "PC Keyboard FAQ" found at: http://www.repairfaq.org/filipg/

Philips has an application note: AN434 Connecting a PC keyboard to the I2C-bus
It can be found at http://www-us.semiconductors.philips.com/handbook/applicationnotes_15.html

Thanks to: Thomas Vegeby <tvegeby(aatt_sign)remotecom.se>

http://www.kvaser.se/can/general.htm

Phillips has several chips - 82c200
Intel 82527 plus a microcontroller w/can onboard
Motorola has a 6805 variant and the 68376
Thanks to: Mike Turner <MikeTurner(aatt_sign)kemet.com>

J1850 is not the same as CAN, but the protocols are conceptually similar. The version of J1850 on the 'B32 is actually the General Motors/Chrysler version of the Society of Automotive Engineers protocol, and it runs at 10.4 kbps (average). It uses VPW (variable pulse width) encoding and requires an external transceiver such as the Motorola MC33390 for talking to the single-wire bus. The transceiver runs from automotive battery (+12 volts nominal). Signals on the bus are at ground and about +7 volts.

(This version of J1850 is incompatible with the Ford version, PWM, which uses a two-wire differential physical layer running at 41.6 kbps.)

A number of different physical layers are possible with CAN. DeviceNet for example runs at 250 kbps using an optically isolated differential transceiver, similar to RS-485. Our company has also done DeviceNet and are working on another new proprietary CAN project.

We have done a number of J1850 projects and can answer more questions if needed. So far I'm not yet aware of anyone's using J1850 outside of automotive. CAN appears to be much more widely used--except by Detroit--and there are signs that CAN may replace J1850 there (but very slowly). CAN is used by some of the European automotive manufacturers and also forms the basis of SAE J1939, used in heavy-duty truck and similar applications.

Both protocols are conceptually similar in that they use CSMA/CD/A, carrier sense, multiple-access, collision detection, arbitration. The network is peer-to-peer and any node can start talking when it senses the bus is free. Any other node with something to say will sync up whenever the first one starts to talk. Physically the bus line (or lines) are wired-OR (active-high or active low, depending on which protocol, which wire), with pull-up or pull-down resistors. One bus state is defined as dominant over the other. The message with the highest priority will dominate any message with a lower priority. Each transmitting node monitors the bus, bit-by-bit, over the first section of each data packet, and if it sees that it has lost arbitration, it quickly stops trying to transmit, and converts itself into a potential message receiver. This system of non-destructive collisions tends to optimize bus bandwidth.

CAN is probably a better choice for a general-purpose network (outside automotive) just because it is widely supported by not only Motorola but also many other chip suppliers. But there is no reason in principle that you couldn't use J1850 for a small local area network. Hope this is helpful.

Thanks to: Kerry Berland <kberland(aatt_sign)ix.netcom.com>

The Texas Instruments "Data Transmission Circuits" data book has a good example of an isolated RS-485 circuit in chapter 5.
Thanks to: Kevin Kostelny-Vogts <kevinkv(aatt_sign)interaccess.com>

• EDN magazine had a recent article with many practical RS-485 application tips, especially with regard to proper termination and drop design. Search http://www.ednmag.com for back articles.
• RS-485 uses RS-422 signaling (electrical) levels, i.e., differential drivers, and twisted pair cable for tx data and rx data. Be sure to terminate each pair with a resistor equal to the characteristic impedance of the cable at each end of the cable and not at the drops.
• Keep the drops very short. The usual practice is to run the cable from point-to- point with effective zero length drops.
• You should be able to run high data rates (19,200 bps+) for long runs (1,000s of feet) with RS-485.

That should handle the hardware considerations, now the real fun begins. The real problems with any communications network(especially multi-drop) revolves around the communications protocol, and especially, procedures for error detection, and retry/correction.

• Error detection requires taking full advantage of the SCI error detection (i.e., parity, framing, etc) and message checksums to detect content errors.
• One of the simpler schemes to digest, conceptually, is the master-slave token ring style network. Basically, one 'hc11 is declared master and the others are declared slaves. The master launches a periodic query which is passed around the network ring checking for any traffic from the slaves. All slaves communicate by adding their message and passing it back to the master. The master serves as a message switch and passes the message on to any slave that needs it. This scheme is best suited to low message load but is completely determinant and avoids all problems if collisions. Another big con is that the loss of any station disables the entire network.
• The other basic scheme is a csma style network where all stations transmit messages as needed. This begs for collisions and leads to many subtle problems related to collision recovery. This scheme is not determinant and is subject to sudden collapse as message traffic increases.

Stepper Motors:
http://www.cs.uiowa.edu/~jones/step/index.html
Thanks to: Michael A. Tyborski <lifetel(aatt_sign)execpc.com>

http://www.radiometrix.co.uk/ They have a good selection of parts.

You might also be interested in the X.10 protocol which is defined so as to deliver messages to other devices via your wall power plugs. Your home power grid becomes a local area net.

A good text book on RF, particularly as it relates to the digital world can be had from the folks at tapr http://www.tapr.org/
Thanks to: Clendon S. Gibson <cgibson(aatt_sign)comp.uark.edu>

USB might tout any number of wonderful bandwidth and performance boosts, but it's damn difficult to interface to unless you use a CPU with a lot of horsepower or dedicated USB silicon. I suspect this is one of the reasons it has not caught on as it's proponents said it would - lowly, slow, antiquated RS-232 is a lot easier for a low-end 8-bit micro to deal with.

USB, from what I've seen, appears to be a classic case of "design by committee", a kitchen-sink effort that attempts to make everybody happy but instead makes nobody happy. Why could they have not left well enough alone and adopted a standard that simply addressed the most pressing and irritating limitations of RS-232, to wit the bipolar signal levels (replace with differential drivers) and the speed limitations (solved by adaptation of the former) ? If really pressed, perhaps adaptation of a synchronous serial approach instead of the more hardware-intensive async method used in RS-232.

The present USB standard, with it's star-hub topology and complex packetization requiring complex silicon to process is not all that attractive to designers of cost-sensitive applications. Why should I buy a $100 USB keyboard when I can get the same thing using the traditional keyboard interface for $25? The same applies to other cost-sensitive devices like mice, modems and monitors - virtually every piece of hardware in the PC realm is subject to fierce competition and cost-sensitivity. A simple topology similar to RS-485 would have done the job quite well - I might not want to connect high-bandwidth multimedia peripherals or mass storage devices to it, but it would have been more than adequate for all the low-end commodity items traditionally interfaced to a serial bus, like keyboards, modems, mice, etc.

There is one computer manufacturer that "got it right" a long time ago - the Apple Desktop Bus shares many of the characteristics (except high bandwidth) that I've discussed above. A simple revamp of this approach that took advantage of the higher-speed serial transmission devices available today would have been completely satisfactory.

The emerging "firewire" standard is a much more appropriate place to apply the additional complexity needed to manage high-bandwidth real-time processing; THIS is the appropriate place to attach mass storage and multimedia peripherals. Mixing both low-data-rate, low cost peripherals like mice, keyboards and monitors along with high-data-rate real-time devices like video cameras and mass storage devices would seem to be folly to me.

Thanks to: Mark Schultz <mschultz(aatt_sign)jps.net>

Question: The preliminary electrical specs for the HC912B32 specifiy a flash program voltage in the range 11.0-11.8V. Anyone out there know whether a standard 12V,5% flash programming voltage generator (e.g., MAX734, MAX662A) will cause problems? It sure would be nice to not have to add all the components to tweak the voltage down a notch.

Answer: Typically Flash is very fussy about Vpp. Excess voltage can cause damage. A three terminal adjustable regulator and two resistors will solve the problem properly. Very simple, very easy. If you have 12 volts available you might consider a Shotkey diode in series in the output (about .3 V drop). (A standard silicon diode, 1N4005, will drop about .6-.7 V) I would add a load resistor to prevent the voltage from soaring under no/light load conditions and improve regulation.

Thanks to: Bob Smith <bobsmith(aatt_sign)i2020.net>

http://www.mcu.motsps.com/cgi-bin/BuildLit.pl?Table=HC12&Type=APP

Programming flash is not quite as simple as programming EEPROM on an HC11 but it is similar. The timing is such that you need to do it from within - ie if you want to do it through BDM you need to load a program into the RAM of the target device that then loads data into the target RAM and finally programs it into the flash. You can get the flash programming details from the HC12 data sheets and from AN1718.
Thanks to: Jim Sibigtroth <rftp70(aatt_sign)email.mot.com>

M68HC12 Code for I2C bus

Download case outlines: http://mot2.mot-sps.com/cgi-bin/cases

No problem unless you want to use the really small SMDs and fine pitched ICs! Remember these components are pretty hardy - in production they go through solder waves for several seconds. It's more likely you'll damage the PCB from heat than the chips.

Quality assurance engineers - do not read beyond this point....

Just use a good temperature controlled iron with a relatively fine tip - not too fine though or it will cool too much at the point. I have used regular solder techniques, as well as solder paste techniques - they both work.

It helps to clean the board very well before hand with a flux remover spray. Using silver loaded LMP solder helps because it melts at a lower temperature, and seems to flow much better. (clean the solder too!).

Using an iron it's fiddly trying to hold the component down, heat one end with the iron, and feed the solder in with your third hand!

If you can get it you can use solder paste - just dab it on the pads, drop the component on, and heat it with a hot air gun (slowly at first to dry the solder pasteand glue the chip down otherwise it will blow away!). You can do lots of components at once this way. (beware the components on the bottom side may fall off). Always use NEW solder paste - after a few months the particles com out of suspension and you get lumps and it doesn't run properly.

Fine pitched ICs are more difficult. It helps to use solder paste, a proper dispenser, and a proper SMD hot air knife with appropriate nozzles. Someone recently mentioned a solder wave process using a soldering iron and a largish tip to drag a blob of solder along over the IC legs, relying on surface tension to leave just the right amount of solder on each connection. Sounds like it needs really well cleaned components and boards and lots of practise!

It also helps if you have a few thousand $$$ for a proper SMD soldering station, but plenty of Radio Amateurs do it with a 40Watt Weller and a paint stripping heat gun....

Thanks to:
Mark Harrison
R&D Engineer
The Bionic Ear Institute
384-388 Albert St., East Melbourne, Victoria, Australia
email: harrisom(aatt_sign)mail.medoto.unimelb.edu.au

I did a small amount of this using Pace equipment. The procedure we used is a bit different. Instead of solder, use solder paste. Solder paste is flux with microscopic beads of solder mixed in. The solder paste is held in small cartridges mounted in a gun, like a miniature caulking gun. The paste should be new or kept fresh in a refridgerator. Instead of using a variable heat soldering iron, use a variable heat hot-air-jet. For the hot-air-jet, we used a Pace vacuum desoldering pencil with the presure reversed so that it blows out a jet of hot air. Turn down the pressure and turn up the heat until the jet of air is hot enough to turn tissue paper brown in just a few seconds. Make sure the smt pads are clean and well tinned. If they are not clean and shiny, use solvent and brush to clean, or tin as necessary. Usually the pads are pre-tinned, and at the most all you would need to do is clean the pads. If you tin yourself, It is impotant that there be just a slight amount of tinning. Remove almost all of the solder after tinning. The pads must be flat and smooth. Squeeze the trigger on the paste solder paste gun and apply a liberal amount of paste to all of the pads, not one pad at a time, just squeeze a continuous bead around covering all of the pads and the space between them. Place the IC onto the pads, close to its final position, push it down into the paste; not hard, you don't want to bend any of the leads. It is not necesary for the IC to be perfectly positioned, get it fairly close. The leads must all be in a plane so that when the IC sits on the board all of the leads touch the board. If some are bent you can fix it later. Move the hot-air-jet around the leads so that the paste starts to melt, then go slower and closer, starting at a corner until the solder melts and move the hot-air-jet along around the IC in one operation. It takes some practice to get the distance, speed, and temperature right. As the paste melts, the solder in the paste will melt too. The molten solder has a high degree of surface tension. The force of surface tension of molten solder is much greater than the viscosity of the now molten flux in the paste. The surface tension of the molten solder will pull the IC leads into near perfect alignment with the pads as you go around. After you have practiced a few times it is quick and easy, much faster and easier than soldering through-hole devices. This works for ICs with any number of pins, it does not work for devices with less than for terminals.

If one of the leads was bent so that it did not get wetted properly, use a wooden soldering aide and a temperature controlled iron. Press down on the lead while you melt the solder; hold the lead down with the soldering aide until the solder solidifies. Sometimes a lead will stick up a small distance, but not enough so that it does not get wetted with solder. As long as it is wetted, you probably have good electrical contact and don't need to fix it.

To desolder, Pace has special attachments for the vacumm desoldering pen. Replace the standard desoldering tip with an smt deslodering tip. You need to use the correct size for the device. The tip is build somewhat like a box so that it touches all the leads of the device at once. Place the desoldering tip over the device and wait till all of the solder melts, then just lift up the tip and the device comes away easily. The device is held to the tip by the force of the vacumm. The tip is constructed so that there is a good seal of high temperature rubber, so that the vacumm is strong enough to overcome the force of surface tension from the melted solder and pull the device away.

Thanks to: Mark Rainess <mrainess(aatt_sign)clark.net>

The solder paste may not work for you: I never tried it for SMT resistors or capacitors but for the larger chips you need alot of practice to get all the contacts soldered properly with no excess solder all over the place.

Apart from the variable heat soldering iron, you'll need a magnifying glass to check if the pads for ICs are soldered properly, a soldersooker (or solder pump) and solder tape stuff (i can't remember the name but it consists of a reel of sorta woven copper ribbon). and a set of tweezers.

* Soldering resistors and capacitors:

melt a small amount of solder onto one pad
holding the chip directly above the pad with the tweezers, heat up the soldered pad with the tip of the soldering iron
place the chip onto the pads, keeping the solder on the pad liquid with the iron
remove the soldering iron but keep the chip in place for a moment
let the chip go
simply solder the opposing side of the chip

* Desoldering resistors and capacitors:

Heat one side of the chip and then the other
press the chip lightly, with the iron, at each side as you heat it.
repeat until the chip moves off the pads
clean up the pads using the solder sooker
NB: often adding more solder to the pads before desoldering makes it easier

* Soldering small ICs (ie 8 to 16 pin) and SM transistor

This is similar to soldering resistors and capacitors
put a dab of solder onto a corner pad (eg equiv to pin-0 on an 8-pin)
put a dab of solder onto an opposing pad (eg equiv to pin-4 on an 8-pin)
holding the IC in the tweezers, line it up over the pads
heat first one soldered pad, attaching the IC at one corner
realign the IC
heat the second soldered pad to keep the IC in place.
solder the remaining pads as you would normally
check for short circuits with the magnifying glass
use the solder tape to remove these [read on further for info on using the tape
check for open circuit
resolder any you find

* Soldering Large ICs

Secure the IC on the PCB in the same way as for a small IC
Now the fun bit:
Cover each pin of the IC in masses of solder, making sure that the pads are covered too.
Use the solder tape to removeall the excess solder
check connection as for small ICs

* Desoldering ICs

This is NOT fun and there is a chance that the IC won't work afterwards.

The procedure is similar to that of removing resistors and capacitors
Again put masses of solder on all the pins
the technique is basically to heat up all the pins so that the solder in liquid around them so that the IC can be moved from position
Run the iron over all the pins, pressing lightly to the side on the pins as you do so.
When enough solder is liquid then the pressure will move the IC off the pads

* Using the solder-tape

This is quite difficult to explain without actually showing you:

	IC 
------------------		put the end of the tape on the pin and
       |     |			pad as shown.
       |     |  <-- pin Heat the end of the tape and the solder /| |\ to be removed simultaneosly | \___/ | <--pad Only the excess solder will be absorbed | ########| into the tape | ########| When no more solder is absorbed or your \######## fingers have been burnt. snip off the ######## used section of tape and continue. ######## <--tape 

Thanks to: J.W.simpson <cnap126(aatt_sign)ccsun.strath.ac.uk>

Home page of IrDA: http://www.irda.org/
Overview paper: http://www.irda.org/use/index.asp

One chip I have used recently is the CS8130 from Crystal Semiconductor Corp. in Austin Tx. This chip provides a neat solution in that all you require is the LEDs (drivers included for 2 LEDs), PIN diode (receiver included), a 3.6864MHz crystal and the serial data.

I've had mine operating over 5 - 6 metres by driving the LEDs hard. HP LEDs HSDL4200 series gives you the highest output that I could find per mA of drive current.

Thanks to: Ian Rumble < Ian_Rumble(aatt_sign)aesprodata.com.au>

Thanks to: Kevin Ross <kevinro(aatt_sign)nwlink.com>

Ceramic capacitors on the other hand have an ESR, but it is not so frequency dependent. They tend to be positioned close to individual chips to provide local decoupling for current spikes generated by logic output stages. CMOS and TTL output stages both generate spikes when both output transistors conduct simultaneously for very short periods on changes of state.

Another use for decoupling is to get rid of power supply noise. Switching converters produce ripple at their switching frequency (typically hundreds of kHz) Parallel capacitance goes some way to eliminate this but ESR prevents it from totally eliminating the noise. I presume that this is what stray 0.1uF caps not immediately associated with any IC are doing.

I've been looking at Sanyo OSCON electrolytics for a new design and they're pretty impressive. The down side is that they are very expensive. To give you an example of how effective: one 22uF OSCON and a TDK common mode choke reduce 200 mV of supply noise at 160 kHz to around 20 mV.

Thanks to: Ted Wood"

Thanks to:David Naviaux <dnaviaux(aatt_sign)rio.com>

X7R, Y5U, and the other dielectrics exhibit much larger piezo effects and TCC. Barium titanate is often used in these dielectrics. That compound is also the main ingredient in most devices deliberately using the piezo effect (grill lighters and sonar transducers). Normally piezo is not a problem unless large forces are involved on the chip and the circuit is high impedance as the piezo voltage is a fairly high impedance signal. Your cap manuf should be able to give some guidance if you have a problem.

Thanks to: Mike Turner <MikeTurner(aatt_sign)kemet.com>

UCN5832A	40DIP	Open Collector (single transistor)
UCN5832EP	44PLCC	Open Collector (single transistor)
UCN5833A	40DIP	Darlington output
UCN5833EP	44PLCC	Darlington output

• Maxim: http://www.maxim-ic.com/
  
• Motorola: http://www.mcu.motsps.com/apps_help/modules/qsm/spi_list.htm
  [Great resource for many types of devices.]

SPI Memories (EEPROM, FRAM, NOVRAM, and SRAM)
=========================================
(# before a part number indicates a new listing as of 04/12/95)

Atmel              AT25C01      1K bit EEPROM
                   AT25C02      2K  "    "
                   AT25C04      4K  "    "
Catalyst           CAT33C704    3-volt CAT35C704
                   CAT35C704    4K  "  EEPROM with security
                   CAT64LC10    1K  "    "
                   CAT64LC20    2K  "    "
                   CAT64LC40    4K  "    "
Harris             CDP68HC68R1  1K  "   SRAM
                   CDP68HC68R2  2K  "    "
Motorola           MCM2814      2K  "  EEPROM
National           NM25C04      4K  "    "
Ramtron            FM2504(0/1)  4K  "   FRAM
                   FM2516(0/1) 16K  "    "
Xicor              X25020       2K  "  EEPROM
                   X25C02       2K  "    "
                   X25040       4K  "    "
                   X25043       4K  "    "    with reset supervisor
                   X25080       8K  "    "
                   X25160      16K  "    "
                   X25320      32K  "    "
                   X25640      64K  "    "
                   X25128      128K "    "
                   X25401      256  "  NOVRAM

http://www.bbsinc.com/iso8859.html has a collection on the ISO8859 (Latin-1) character set. Includes ASCII tables, tables of control characters, and links to ISO8879 and UNICODE info.

Take a look at:
http://www.sensoryinc.com
http://www.rcsys.com
http://www.isd.com/

Here are a couple of pages that describe how to care for NiCad batteries:

http://www.gobattery.com/maintenance.html
http://www.ccrane.com/nicadlit.htm
Maha NiMH Batteries

If you're interested in robotics (particularly in using Motorola microcontrollers in robotics), I suggest you visit the University of Florida Machine Intelligence Laboratory website at http://www.mil.ufl.edu. We're a graduate and undergraduate robotics and artificial intelligence research laboratory. Of particular interest to someone getting started in robotics, we teach a class called IMDL (Intelligent Machine Design Lab http://www.mil.ufl.edu/imdl/). Students with no prior experience in robotics build a robot during a semester. All their papers are on the website, so you can look there for ideas, sensors, things we know work, and pitfalls to avoid. We'd be happy to hear any ideas you come up with and help with problems you get stuck on. Good luck!
Thanks to: Matt Radlinski mattrad(aatt_sign)mil.ufl.edu
University of Florida
Machine Intelligence Laboratory
and the M68HC12 mailing list

Harris SP720 http://www.Littlefuse.com/

What is the SP720. It is a 16-pin package with 14 protection circuits. They are like the traditional dual-diode input protection except that they use transistors as SCR's to get very fast inputs. Perhaps a more convenient part is the SP724 which has four protection circuits in a 6-pin SOT-23 package. Both Arrow and Avnet appear to have some, but they want to sell reels of 3K parts. These quad parts are VERY attractive compared with dual diodes in SOT-23.
Thanks to Gene Zumchak [zumchak(aatt_sign)cerg.com]

Here are some PDF files and other links to metastability information:

• Discussion from the Electronic Muse
• Metastable Response in 5-V Logic Circuits from TI
• Metastability Considerations - Xilinx App Note XAPP077
• Metastability Recovery - Xilinx App Note XAPP094
  
• There are many more great references on the web. Try a search using http://www.coogle.com