PCT
`
`WORLD INTELLECTUAL PROPERTY ORGANIZATION
`International Bureau
`
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(51) International Patent Classification 5 :
`H04B 1/00, 7 /00, G06F 7 /00
`H04B 14/04
`
`Al
`
`(11) International Publication Number:
`
`WO 90/06633
`
`( 43) International Publication Date:
`
`14 June 1990 (14.06.90)
`
`(21) International Application Number:
`
`PCT/US89/05579
`
`(22) International Filing Date:
`
`8 December 1989 (08.12.89)
`
`(30) Priority data:
`283,425
`282,819
`283,534
`282,402
`282,008
`283,427
`282,406
`283,140
`282,417
`283,428
`283,554
`283,426
`282,792
`283,549
`282,410
`
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`9 December 1988 (09.12.88) US
`
`(60) Parent Applications or Grants
`(63) Related by Continuation
`US
`283,425 (CIP)
`Filed on
`9 December 1988 (09.12.88)
`US
`282,819 (CIP)
`9 December 1988 (09.12.88)
`Filed on
`US
`283,534 (CIP)
`9 December 1988 (09.12.88)
`Filed on
`US
`282,402 (CIP)
`9 December 1988 (09.12.88)
`Filed on
`US
`282,008 (CIP)
`9 December 1988 (09.12.88)
`Filed on
`US
`.
`283,427 (.CIP)
`Filed on·
`9 December 1988 (09.12.88)
`US
`282,406 (CIP)
`9 December 1988 (09.12.88)
`Filed on
`US
`283,140 (CIP)
`9 December 1988 (09.12.88)
`Filed on
`US
`282,417 (CIP)
`9 December 1988 (09.12.88)
`Filed on
`US
`283,428 (CIP)
`(54) Title: MICRO POWERED RF DATA MODULES
`
`Filed on
`us
`Filed on
`us
`Filed on
`us
`Filed on
`us
`Filed on
`us
`Filed on
`
`9 December 1988 (09.12.88)
`283,554 (CIP)
`9 December 1988 (09.12.88)
`283,426 (CIP)
`9 December 1988 (09.12.88)
`282,792 (CIP)
`9 December 1988 (09.12.88)
`283,549 (CIP)
`9 December 1988 (09.12.88)
`282,410 (CIP)
`9 December 1988 (09.12.88)
`
`(71) Applicant (for all designated States except US): DALLAS
`SEMICONDUCTOR CORPORATION [US/US]; 4350
`Beltwood Parkway South, Dallas, TX 75244 (US).
`
`(72) Inventors; and
`(75) Inv.entors/ Applicants (for US only) : LEE, Robert, D. [US/
`US]; 916 Linwood, Denton, TX 76201 (US). DIAS, Do(cid:173)
`nald, R. [US/US]; 2217 Via del Norte, Carrollton, TX
`75006 (US). MOUNGER, Robert, W. [US/US]; 4280
`Trinity Mills Road, 143507, Dallas, TX 75252 (US).
`BOLAN, Michael, L. [US/US]; 6214 Misty Trail, Dal(cid:173)
`las, TX 75248 (US). HEPTIG, John, Patrick [US/US];
`7000 Treehaven, Fort Worth, TX 76116 (US). KUR(cid:173)
`KOWSKI, Hal [US/US]; 4208 West Creek Drive, Dal(cid:173)
`las, TX 75252 (US). KLUGHART, Kevin, M. [US/US];
`3721 Spring Valley Road, 143131, Dallas, TX 75244
`(US).
`
`(74)Agent: GROOVER, Robert, III; Worsham, Forsythe,
`Sampels & Wooldridge, 2001 Bryan Tower, Suite 3200,
`Dallas, TX 75201 (US).
`
`(81) Designated States: AT (European patent), BE (European
`patent), CH (European patent), DE (European patent),
`ES (European patent), FR (European patent), GB (Eu(cid:173)
`ropean patent), IT (European patent), JP, KR, LU (Eu(cid:173)
`ropean patent), NL (European patent), SE (European
`patent), US.
`Published
`With international search report
`
`(57) Abstract
`
`+ 3 VOLT
`Ji LITHIUM
`250 -: BATTERY
`
`VsAT veeo
`
`vee
`0S1203
`Fl
`
`A+
`
`210
`
`230
`
`vee
`DS1204
`VsAT
`
`122
`
`A low-power wireless data
`communication system, in which
`base stations (110) can automati(cid:173)
`cally interface to batter-powered
`portable data modules (210) as
`they are brought within range. In
`the data modules (210), each re(cid:173)
`ceive antenna (121)
`is directly
`connected to a gain-controlled
`comparator (420A, 420B). Band(cid:173)
`is accom(cid:173)
`pass filtering (448)
`plished economically by use of
`simple digital circuits. The two-le•
`vel digital output from the com•
`parator
`(420A, 420B)
`is
`fed
`(through an intersymbol detector,
`a counter, and a ripple-through
`magnitude comparator) to a state
`machine (552), which decodes the resulting digital waveform to a conventional serial-bus format. The internal data bus (701D)
`provides an interface to memory chips (262) and (optionally) to other chips, such as an electronic key. The decoder chip (220) al(cid:173)
`so provides a secondary power supply to the other chips (230), and modulates the power supply (250) to assist detection of trans(cid:173)
`itions on the reset-bar line of the serial bus (206). The modules (230) use widely different frequencies for read and write opera(cid:173)
`tions. (Transmissions by the base station (110) use a pulse-width modulation scheme where the most commonly used signals
`correspond to the shortest pulse. A "read" command is encoded as the same pulse width as one of the two write commands). In
`addition, a pair of touch contacts (270) can be used to override the RF link. Error-checking (Fig. 7E) is performed on incoming
`commands before memory access (260) is permitted. "Freshness seal11 logic (510) prevents any battery drain until the module is
`initially turned on (by placing it in a strong field).
`
`2 kHz FRESHNESS INPUT
`
`240
`
`RF OVERRIDE
`
`270
`
`300 MHz
`TRANSMITTER
`
`300 MHz TRANSMIT ANTENNA
`
`Page 1 of 142
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`GOOGLE EXHIBIT 1008
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`

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`i
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`i
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`f
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`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCT on the front pages of pamphlets publishing international
`applications under the PCT.
`
`Austria
`AT
`AU
`All#l'lllia
`Barbados
`BB
`Belgi.tm
`BE
`BF
`Bwtina FIISIO
`BG Bu.-na
`Benin
`BJ
`BR
`BtilZil
`CA
`Canada
`Central Aftic:an Republic
`CF
`Congo
`CG
`Swiacrland
`Qi
`CM Cameroon
`DE Gmnany, Federal Republic of
`DK
`Denmark
`
`Spllin
`ES
`FT
`rmlatld
`France
`FR
`GA Gabon
`GB United Kingdom
`HU Hunpry
`rr
`Italy
`Japan
`JP
`KP Democratic People's Republic
`of Korea
`KR
`Republic of Korea
`u
`Liechtcmtein
`Sri Lanka
`l.K
`w Luxembourg
`MC Monaco
`
`MG Madagascar
`ML Mali
`MR Mauricania
`PINI Malawi •
`NL
`Netherlands
`NO
`Norway
`RO
`Romania
`SD
`Sudan
`SE
`Sweden
`Senegal
`SIi
`Soviet Unbn
`SIJ
`m Chad
`Togo
`TG
`us
`U nitcd States of America
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`Page 2 of 142
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`WO 90/06633
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`MICRO POWERED
`RF DATA MODULES
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`BACKGROUND AND SUMMARY OF THE INVENTION
`The present invention relates to wireless data interface systems, and
`to portable data modules for use within such a system, and to power(cid:173)
`efficient integrated circuits.
`Systems which can provide short-range wireless data communication
`between a base station and a portable low-power module have recently
`been the subject of development efforts by a number of groups. Such
`systems can be extremely useful in many contexts, such as control of
`personnel access to secure facilities, medical monitoring of inpatients,
`automated livestock management, automated manufacturing generally,
`inventory control, theft controi and others described below.
`There are many uses for low-powered RF receivers, in such systems
`and elsewhere. Due to the legal constraints of spectrum allocation, many
`short-range data links must use extremely small RF signal levels.
`25 Moreover, in many cases the transceivers used for such communication
`must operate with minimal power drain, including minimal standby power.
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`It is very difficult to satisfy the objectives of low power consumption while
`also providing adequate sensitivity and noise rejection.
`However, such a system is subject to many constraints.
`If the
`portability of the portable stations is to be maximized, the battery weight
`s must be small. This means that the power consumption of the portable
`module - in active or in standby mode - must be exceedingly low.
`Moreover, many possible applications are highly cost-sensitive.
`In most applications, rechargeable batteries are not suitable for a
`power supply. Rechargeable batteries not only impose a user burden (to
`perform recharging), but also tend to have electrical characteristics which
`may be dependent on the discharge/recharge history of the particular
`battery. Many possible applications cannot tolerate such uncertainty, and
`require a degree of reliability which demands a very conservative approach
`to power supply design and rating.
`Greater noise immunity can be achieved by using high transmitter
`power, by by using large, highly directional, and/or highly resonant
`), or by using narrow-bandwidth
`antennas (which provide 11antenna gain11
`filtering ( or more sophisticated signal processing operations) in the
`receiver (which provide 11processing gain"). However, due to the
`constraints on the total power budget in a portable data module, and due
`to the legal constraints mentioned above, higher transmitter power is often
`not an option. Moreover, directional antennas are also impractical for
`many systems. Moreover, processing gain is also not free: processing gain
`is most easily achieved by precise knowledge of the characteristics of the
`expected signal, and/or by extensive computing operations on the
`recovered signal. Precise knowledge of signal characteristics tends to
`require precise knowledge of time and/or frequency, and maintaining this
`knowledge also consumes power. Thus, adding processing gain into a
`portable data module not only increases the capital cost, but also places
`an additional burden on the power budget. Thus, while successive
`engineering improvements can provide some increase in noise immunity,
`the room for improvement is inherently limited.
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`The result of these constraints is a severe squeeze on the system
`designer: sensitivity must not be too low, and the immunity to electrical
`noise must be good, and the power consumption must be ver:y low. Such
`systems may sometimes need to operate in high-noise environments, and
`such environments may completely block the communications channels.
`In a micropowered system, where the transmitter powers may be of the
`order of a few milliWatts to a few Watts, noise sources may sometimes
`provide an RF power level, at the receiver, within the reception band,
`which is comparable to the power level provided by the transmitter. For
`example, in manufacturing environments, extremely high broad-band noise
`levels may be generated by arc welding ( or arc furnaces), by plasma
`deposition processes, by large motors, or by digitally controlled actuators.
`In such applications, it would obviously be undesirable for the wireless
`data link to shut down when an extended period of high noise occurs. For
`another example, in a military system which controls entry to secured(cid:173)
`access facilities, it would obviously be unacceptable for the access control
`system to shut whenever a high level of electrical noise occurred, ~ due
`to high-powered radar or communications activities.
`Therefore, for
`system "robustness, 11 it is highly desirable that such systems should be able
`to operate under high-noise conditions.
`In many such applications, the size and weight of the portable module
`is an extremely sensitive issue. A module which is merely transportable
`will not suffice. For example, pagers and portable radios have often had
`weights of 10 ounces or more, and volumes of 10 cubic inches or more.
`25 H modules of this size were used ( for example) for patient identification
`in a hospitals, the patients would unload such cumbersome objects as
`quickly as possible, by any means possible. Similarly, in many applications
`such large modules could not be used for inventor:y control, since there
`would be no convenient place to put them, and they would easily be
`damaged ( or personnel would learn to bypass them).
`The need to conserve power act1.1ally implies several separate
`constraints: the consumption requirements of both the active and the
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`standby mode must be separately minimized, and the issues to be
`considered are somewhat different.
`The most difficult issues are presented by the standby mode. The
`portable module cannot afford the power to continually broadcast a
`5 beacon, but, even if the base station module broadcasts a beacon to
`ascertain
`the possible presence of receiver modules,
`the power
`requirements of listening for such a beacon are large.
`Suppose, for example, that a portable data module, with non•
`rechargeable batteries, is desired to have a lifetime of at least 10 years,
`and to be able to perform at least 1,000,000 data transactions during its
`(This is an extremely aggressive set of specifications, and is
`lifetime.
`believed to be far beyond the capabilities of any system presently
`available.) Suppose further that the available battery energy is 2000
`Joules (1 milliAmpere for 190 hours at 3 Volts). Then the power
`dissipation in the standby mode must be no more than several millionths
`of a Watt, or all of the battery energy will be dissipated merely in waiting
`for the active communication transactions to begin, before the design
`lifetime· has expired. The present· application discloses several novel
`teachings which are directed to this aspect of power conservation.
`The power efficiency requirements of battery-powered modules can
`be extremely stringent. For best reliability, neither battery recharging nor
`user detection of imminent failure should be relied on. Therefore, to
`reliably meet the design battery lifetime of a module, extreme care must
`be taken to identify and control the worst-case battery-drain scenarios.
`Battery lifetime management can be particularly difficult where several
`complex integrated circuits are included in a battery-powered module.
`Where significant control interactions, or even data exchange, may occur,
`the demands of such transactions must also be allowed for.
`Some previously proposed methods for implementing such wireless-
`access data systems have used passive components _ for RF detection,
`connected so that the RF power received from the base station can
`actually provide the necessary power to operate the remote module. Such
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`systems require that the RF power level at the receiver must be far higher
`than would be needed merely for communication.
`Power conservation also affects the choice of coding scheme. The
`energy per bit of data successfully sent to the base station, and per bit of
`data correctly received from the base station, must both be minimized
`under the conditions actually expected (including distance from remote to
`base module, RF noise level, and the lengths of data streams which
`typically need to be handled).
`A systems which provides a wireless data-transfer interface to portable
`data modules has the potential for great flexibility. However, the high(cid:173)
`level organization of such a system must also be considered carefully. The
`communications protocols often assign the base station to be the master
`station.
`In such a typical configuration of this kind, each base station
`( unless passwording prevents this) can query, read, and write data to any
`portable module which may happen to be in range, without any
`independent action at' the remote module.
`A large system of this kind presents issues of access collision. If a
`large number of modules are within a base station''s range," the base
`station may receive responses from many portable modules when it
`broadcasts a query signal. Each module has a 11name11 by which i! can be
`addressed separately, but the use of module identifiers does not remove
`all problems: if a large number of modules may be present in the total
`system, the time for a base station to query the possible module identifiers
`may be large.
`Modern semiconductor technology has provided solid-state memories
`with such low standby power requirements that a single coin-sized battery
`can power the memory for ten years of lifetime or more. Such memories
`are already commercially available. However, if a high volume of such
`memory could be used in a portable wireless-accessible module, the
`functionality of such modules could be tremendously increased. However,
`presently available techniques tend to lead to low maximum data rates.
`With the constraints discussed above, this means that, while it is easy to
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`accumulate a large volume of data, it is not so easy to download that data.
`However, for many applications it would be quite desirable to be able to
`perform a block 11dump11 of memory.
`Error-check-and-correct protocols are commonly used to preserve data
`integrity. However, in a wireless data communication system, which
`inherently has a ·high exposure to noise, one important class of error must
`be carefully avoided: if a write were to be directed to the wrong location
`in the module's memory, data integrity would be lost, even though the
`error checkbits for • the data stream all indicated that no error had
`occurred.
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`Multiport Memory
`As is well known to those skilled in the art of computer system
`architectures, multiport memories are a very useful basic tool. A
`11multiport11 memory is one in which different computer processes can
`independently access a common memory space, through hardware
`channels which are at least partly separate. Multiport memories are
`generally useful for flexible buffering of data transfers .• For example, they
`can be used to pass data between two processes which are independently
`clocked, or clocked at different frequencies.
`The most straightforward way to achieve multiport functionality is by
`using memory chips which actually have independent data paths to each
`cell. (For example, a two-port SRAM of this type would have two pairs
`of pass transistors in each cell, and would be connected to two wordlines
`( one for each of the pass transistor pairs), and would also be connected
`to two bitline pairs. However, this approach does not scale well as the
`number of ports increases.
`An alterp.ative approach to multiport memory is to use a simple
`memory array (e.g. singleGported or dual-ported), with memory controller
`logic which arbitrates access to the array. (The memory controller logic
`30 may be on a separate integrated circuit, or may be integrated with the
`memory cells.) In such architectures, it may sometimes be necessary for
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`a port to wait until access is available, but the multiport functionality can
`still be achieved.
`
`Adjusting analog circuits
`The closed-loop gain of an amplifer gain stage is normally adjusted
`using a resistor ratio. (That is, when a feedback resistor RF is interposed
`in the feedback path from the output terminal to the negative input
`terminal of a differential amplifier, and an input resistance Rm is
`interposed between the negative input terminal signal and an incoming
`signal Vin' the voltage gain V outN in will be equal to the ratio of the
`resistances -RpfRm-)
`Many methods are known for trimming resistor values, to adjust the
`closed-loop gain of an amplifer. Such trimming methods will typically
`involve applying a laser beam to reduce the linewidth of a thin-film or
`thick-film resistor.
`Closed-loop amplifier stage gain values are adjusted, in some
`embodiments of the invention, by selecting components which have values
`scaled in powers of two. For example, if the smallest available value of
`the feedback resistor is Rf,o, thin film (polysilicon) resistors would be
`provided with values of 2Rt,o, 4Rr,o, 8Rt,o, etc. Similarly, if the smallest
`available value of the input resistor is Rm,o, then additional resistors would
`preferably be provided with values. of 2~,o, 4Rin,o, 8~,o, etc. (Note that
`the minimum resistor values Rr,o and ~.o do not have to be equal.) This
`provisioIJ. of selectable digital increments means a desired closed-loop gain
`can be "dialed in" directly, by translating a desired ratio into two binary
`numbers.
`The presently preferred embodiment provides such digitally scaled
`values not only for resistors, but also for capacitors. The trimmable
`resistors and capacitors are adjusted to set both the center frequency and
`Q of a bandpass filter. The mathematical relations which define the
`center frequency and Q of an active RC filter as a function of the
`component values used are very well known to those skilled in the art.
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`However, the use of digitally scaled selectable components, so that the
`desired component values can be directly "dialed in," is believed to be
`new in the art.
`As is well known to those skilled in the art, the value of a thin film
`resistor can be changed by changing the width/length ratio of a layer of
`a given sheet resistance, by changing the film thickness of a material of a
`given resistivity, by modifying the thin film layer so that it has a different
`sheet resistance (e.g. implanting it with a dopant), or by substituting a
`material with a different sheet resistance. The preferred embodiment
`simply uses pattern modifications, to provide a variety of width/length
`ratios. This idea is particularly useful where high-gain amplifer stages may
`be needed.
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`Filterinfi
`Filtering electrical signals is one of the most basic operations in
`electronics. Typically :filtering functions will be defined with reference to
`the :frequency domain. For example, if a complex signal is passed through
`a "low-pass" filter, only those signal components which are ·below a certain
`frequency will pass through the filter. Similarly, a 1'bandpass" filter will
`pass only those signal components which are within a range of frequencies
`around a center frequency. (The 1'bandwidth11 of a bandpass filter specifies
`how wide this range of frequencies is.) The :filtering characteristics of an
`electrical circuit will be determined by the values and interconnections of
`the active and passive components used.
`A filtering characteristic may be implemented in a wide variety of
`25 ways. The different possible implementations can differ in many respects.
`For example, where active devices are part of the filter, the power
`consumption of different implementations may vary. The sharpness of the
`boundaries between the passband and stopband may also vary.
`(For
`example, a very simple passive filter, which includes only one capacitor
`and one inductance in series, will typically have a slope of about 6 dB per
`octave at the passband edges. Thus, the wider the passband, the less
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`sharp the passband edges will be. For many applications a sharper slope
`is needed. More complex circuits can provide much sharper slopes.)
`Different implementations may also differ in their area requirements,
`sensiti'?ty to parameter variation, passband ripple, maximum attenuation,
`insertion loss, practicable frequency range, etc.
`Digital signal processing ("DSP") can be used to readily implement a
`very wide variety of filter functions. However, unless the system design
`already
`includes a microprocessor or specialized DSP unit, and
`digital/analog a.Iild analog/digital converters, a substantial amount of
`hardware must be added before DSP techniques can be used. Moreover,
`DSP is likely to consume relatively large amounts of power, and may
`generate significant amounts of electrical noise.
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`Battery-backed Microprocessor
`In addition, microprocessors which can operate on extremely low
`power are also now available. An important example is the DS5000,
`available from Dallas Semiconductor Corporation, Dallas, Texas. (This
`chip, and its description in the data books of Dallas Semiconductor
`Corporation, are hereby incorporated by reference.) This microprocessor
`• can operate with very low power consumption in active and standby
`20 modes. The power consumption is so small that this microprocessor can
`be used in an extremely compact module powered by a very small lithium
`battery, and still have good operating lifetime.
`Such microprocessors can be useful in a very wide variety of applica(cid:173)
`tions, and it would be very useful to be able to make use of them in a
`portable wireless data module. The present invention provides a system
`architecture, for a 11smart11 portable wireless module, in which a large
`volume of memory space is shared by a microprocessor ( or other complex
`chip) and by the demands of wireless access.
`It should be noted that microprocessors are not the only type of
`integrated circuit which the present invention helps to integrate into a
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`portable data module. Different chips ( and/or multiple chips) can be
`used. For example, display drivers can also be connected to memory
`through a high-data-rate internal bus. For another example, customized
`signal processing chips, adapted to functions such as speaker identification,
`can also be used. More exotic chip types, such as neural networks or
`cellular automata, can also be used (in suitably low-power versions).
`It should also be noted that the disclosed novel memory controller is
`not applicable only to portable modules, nor even to low-power
`applications generally. The innovative teachings herein can provide
`improved access arbitration between serial and parallel ports, wherever a
`multiport interface to serial and parallel ports is used. Thus, for example,
`this controller architecture could also be used in much higher-data-rate
`environments.
`Error-check-and-correct protocols are commonly used to preserve data
`integrity. However, in a wireless data communication system, which
`inherently has a high exposure to noise, one important class of error must
`be carefully avoided; if a write were to be directed to the wrong location
`in the module~s memory, data integrity would be lost, even though the •
`error checkbits for the data stream all indicated that· no error had
`occurred.
`The presently preferred embodiment provides an architecture wherein
`a substantial amount of random-access memory (RAM) is included in the
`remote module. This presents data-integrity problems which are quite
`different from those presented by the more common use of a small
`amount of memory: if an error occurred in the address field, during a
`write to the RAM, data could be lost. To ensure data integrity, a serial
`access protocol is used to control wireless accesses. Since the data rate
`of wireless access is rather slow, a special command is added to this
`protocol to accelerate access arbitration between wireless accesses to
`30 memory and the higher-bandwidth internal accesses.
`As. described in detail below, the memory controller chip of the
`presently preferred embodiment provides dual-port access to single-port
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`memory, where one of the two ports is serial and one is parallel. In the
`presently preferred embotj.iment, an arbitration byte is used to avoid
`conflicts between the two ports. (Some bits of the arbitration byte can be
`written only by the serial port, and some bits can be written only by the
`parallel port.) In the presently preferred embodiment, the serial port
`always has priority for access to the memory. Normally, in a multiport
`memory organization of this kind, the serial port would read, write, read
`the arbitration byte to check for no access collision. However, due to the
`overhead imposed by the 56-bit access protocol used in the presently
`preferred embodiment, such a series of accesses would require 192 serial
`bits (56+8 + 56+8 + 56+8), which is slow.
`Instead, the present
`invention uses a special protocol (for this purpose only), which compresses
`the normal serial access protocol· so that the serial port will read 8 bits ( of
`the arbitration byte), write 8 bits, and read 8 bits, within a single access.
`15 Thus, instead of 192 bits of overhead, only 80 ( 56 + 8 + 8 + 8) are
`required.
`For long lifetimes, a prime determinant of the lifetime is the power
`consumption when the integrated circuit is idle. For example, even a few
`microAmperes of standby current will exhaust a 2000-Joule battery within
`a ten-year lifetime. Various design techniques can be used to reduce
`st~dby current, but the system designer can readily find other uses for
`any excess battery capacity. (For example, other functions may be added,
`or longer lifetimes specified, or smaller batteries used.) Since standby
`power consumption is a significant factor in design lifetime, the design
`lifetime must normally be dated from the time when standby power
`·consumption begins.
`This is generally undesirable. The customer needs to know the
`lifetime from the time when he gets the part. To provide customers with
`this assurance, the manufacturer and distributors must therefore control
`the distribution chain so that the maximum time in inventory is known,
`and the design lifetime for the part must be reduced to allow for this
`maximum time in inventory. This is inconvenient.
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`Moreover, in some applications a long inventory time is highly
`desirable. For example, in military or industrial applications it might be
`useful to keep a stock of "field spares" on hand, very close to the actual
`installation, so that a failed electronic module could be rapidly replaced.
`The present invention provides a way to totally inactivate ( or
`reactivate) a sealed integrated circuit module, without using any
`mechanical elements which might fail, or using any electrical contacts
`which might burden the hermeticity of the module packaging.
`The present invention provides a micropowered module containing
`one or more integrated circuits and a battery. The module is originally
`in a state of zero power consumption. When the module is to be put into
`use, a very strong electromagnetic field is applied at a predetermined
`frequency. (For example, the user can hold the module between the poles
`of a C-shaped solenoid which is being driven by a significant current at
`the appropriate frequency.) A very small and simple antenna is used to
`.
`receive this energy. The output of this antenna is, in the presently
`preferred embodiment, connected directly to the input of MOS logic gates,
`so that no current flows unless the incoming signal reaches a high enough
`voltage to switch the MOS transistors. A preset pulse code at this
`frequency will be detected by subsequent logic elements, and will change
`the status of a stored bit which identifies whether the integrated circuit
`should be turned off (i.e. in "sleep" mode) or on. (While the integrated
`circuit is on, it may be in active or standby mode. This is determined by
`other logic, and is separate from the operations described.) In standby
`25 mode, the power from the battery will avoid data loss.
`The lithium batteries preferably used have a very long shelf life, so
`that the time when the module is in sleep mode does not subtract from
`the design lifetime. Thus, the manufacturer can ship modules which are
`in sleep mode, and the customer ( or distributor) can activate the modules
`30 when they are nearing use.
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`Only one chip in a module norm.ally needs to have this sleep and
`wake capability. This chip can provide a control signal or a power supply
`output to the other chips accordingly.
`In the presently preferred embodiment, the wireless "freshness seal"
`command can be used to command the module to wake up or to
`command it to go back to sleep. Thus, a user who foresees a long idle
`time for a module can cause the module to go back into a zero-power(cid:173)
`consumption mode until needed.
`The present invention is particularly advantageous in a wireless-access
`data module, since the module can be made totally hermetic. However,
`this wireless freshness seal is also advantageous in other module
`configurations too. The lack of external switches or contacts improves the
`reliability of the module. Moreover, the fact that the freshness seal
`switching is not readily apparent may prevent unsophisticated users from
`inadvertently activating it, and losing functionality or stored data.
`Of course, a wide variety