Abstract:
A worldwide logistics network includes a processing center for receiving customer orders for crystal oscillators over communications links, processing the orders, and generating work orders that are selectively disseminated over communications links to programming centers at strategic locations around the world. Each of the programming centers carries an inventory of generic programmable crystal oscillators. Upon receipt of a work order, a programming center withdraws quantity of programmable crystal oscillators from inventory sufficient to fill the customer order, and, using automated parts handling equipment, the oscillators are successively directed to an interface position with a computer. There, the unique crystal frequency of each oscillator is read and each oscillator is uniquely programmed on the basis of its crystal frequency to generate an output frequency meeting customer specification. Upon completion of this final manufacturing step, the programmed crystal oscillators are shipped to the customers directly from the programming centers.

Description:
REFERENCE TO RELATED APPLICATION 
     This application is a division of application Ser. No. 09/304,820, filed May 5, 1999, now abandoned, which is a continuation of application Ser. No. 08/795,980, filed Feb. 5, 1997 (now U.S. Pat. No. 5,960,405), both of which are incorporated in their entirety herein by reference. This application is also related to applicants&#39; U.S. application Ser. No. 08/795,978 (now U.S. Pat. No. 5,952,890), entitled “Programmable Crystal Oscillator”, filed Feb. 5, 1997, incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to crystal oscillators and more particularly to the marketing of crystal oscillators drawn from inventory on demand and frequency programmed to customer specification as the final production step in their manufacture. 
     BACKGROUND OF THE INVENTION 
     Oscillators are ubiquitous components utilized for timing purposes in virtually all forms of electronic hardware ranging from timepieces to computers. Unfortunately, timing frequencies of the oscillators vary widely depending upon application and the particular electronic hardware in which the oscillators are to be implemented. 
     The most popular type of oscillator is a crystal oscillator, and, consequently, they are in high demand. Unfortunately, crystals, the heart of every crystal oscillator, are difficult to manufacture and require a long leadtime. In this process as traditionally practiced, a crystal bar or ingot is grown from a seed crystal. The crystal bar is x-ray examined to determine the correct cut angle, mounted at that angle on glass in a cutting fixture, and then sliced into crystal wafers. The wafers are then x-ray examined to confirm the cut angle. Next, the wafers are gross lapped to an appropriate thickness and then divided to remove the crystal seed. The wafers then undergo a series of steps, including x-raying, waxing together, shaping, unwaxing, intermediate lapping, segmenting into individual crystal blanks, fine lapping, chemical etching, sorting, gross base plating and multiple final plating steps, all designed to condition the crystals to generate a source (resonant) frequency to customer specification. This process may take weeks. Moreover, it must be known early in the manufacturing process, e.g., prior to intermediate lapping, but in some cases prior to slicing the ingots into wafers, what source frequencies the crystal wafers must generate in the customer end product. Thus, customers typically cannot order custom crystal oscillators from a manufacturer&#39;s inventory, i.e., crystal oscillators generating custom frequencies rather than stocked standard frequencies. In the case of custom crystal oscillators, customer orders are typically placed before a manufacturer will begin manufacture. If the manufacturer has a backlog of customer orders, it is not uncommon that the leadtime for custom crystal oscillators from order placement to delivery is measured in months. To gain shorter leadtimes, customers will typically have to pay premium prices. It is also not uncommon that, after placing a long leadtime order with a manufacturer, the customer&#39;s frequency specification changes or even the need for the crystal oscillator disappears. If manufacture of the oscillators to fill the order has begun, the customer is typically subjected to cancellation charges, since crystal wafers and the associated integrated circuit may not be salable to future customers. Consequently, these components may eventually have to be reworked or simply scrapped. 
     SUMMARY OF THE INVENTION 
     It is accordingly an objective of the present invention to provide a wide area, e.g., worldwide, logistics network for marketing crystal oscillators that overcomes the disadvantages and drawbacks of traditional crystal oscillator marketing practices, most particularly in reducing leadtimes to days, as contrasted to weeks or months. 
     To achieve this objective in accordance with one aspect of the present invention, there is provided a method of manufacturing and distributing crystal oscillators in response to customer demand, comprising the steps of establishing a centralized order process center; establishing a plurality of oscillator programming centers at geographically diverse sites linked to the process center by a communications network; and manufacturing a supply of generic programmable oscillators at a production site. The generic programmable oscillators are then distributed amongst the programming centers to build up and maintain an inventory of generic programmable oscillators at each programming center site while customer oscillator orders are accepted at the order processing center for processing to identify specifications of each processed customer order. The customer specifications, including oscillator quantity and output frequency, and delivery date and destination, are communicated as work orders to selected programming centers based on capability to meet the customer order specifications. Each programming center, in response to receipt of a work order, performs the steps of withdrawing from inventory a quantity of generic programmable oscillators sufficient to satisfy the oscillator quantity specified in the received work order, programs each generic programmable oscillator to generate the output frequency specified by the received work order, and ships the programmed oscillators to the delivery destination specified by the received work order. 
     In accordance with another aspect of the present invention, there is provided a method of manufacturing crystal oscillators to diverse customer specifications, comprising the steps of producing a supply of programmable crystal oscillators that generate clock signals of randomly differing frequencies; maintaining an inventory of the programmable crystal oscillators; and withdrawing from the inventory a plurality of the programmable crystal oscillators sufficient to satisfy a quantity of crystal oscillators specified in a customer order. Each of the plurality of programmable crystal oscillators is powered up to read the frequency of a reference clock signal output by the programmable crystal oscillator and then uniquely programmed on the basis of the reference clock signal frequency reading to produce an output clock signal frequency specified by the customer order. 
     Additional features, advantages and objectives of the present invention will be set forth in the description that follows and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and advantages of the present invention will be realized and obtained by the apparatus particularly pointed out in the following written description and the appended claims, as well as in the accompanying drawings. 
     It will be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     The accompanying drawings are intended to provide a further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate a preferred embodiment of the invention, and together with the description, serve to explain the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of a programmable crystal oscillator utilized in the present invention; 
         FIG. 2  is a block circuit diagram of the programmable crystal oscillator seen in  FIG. 1 ; 
         FIG. 3  is a block circuit diagram showing details of the frequency multiplier utilized in the programmable crystal oscillator of  FIG. 2 ; 
         FIG. 4  is a functional block diagram of a worldwide logistics network for marketing the programmable crystal oscillator of  FIG. 2 ; 
         FIG. 5  is a schematic block diagram of one of the programming centers in the network of  FIG. 4 ; 
         FIG. 6  is a flow chart illustrating a presently preferred method of programming the crystal oscillator of  FIG. 2  in the programming center of  FIG. 5 ; and 
         FIG. 7  illustrates a form of programming data word utilized in the programming method of claim  6 ; and 
     
    
    
     Corresponding reference numerals refer to like parts throughout the several figures of the drawings. 
     DETAILED DESCRIPTION 
     An embodiment of a programmable crystal oscillator, utilized in the present invention, is illustrated in FIG.  1 . This oscillator  20  may be produced in a variety of industry standard sizes and in two basic package configurations, pin through and surface mounted (SMD), depending upon the manner in which the oscillator is to be mounted in its particular application. The illustrated embodiment has six input/output (I/O) terminals, consisting of a Signature clock terminal  21 , a dedicated Program input terminal  22 , a ground (VSS) terminal  23 , a supply voltage (VDD) terminal  24 , a Signature output terminal  25 , and a programmed frequency clock signal output (F out )/programming clock pulse input (CLK in ) terminal  26 . As will be described in detail below, programming data is entered via dedicated Program terminal  22  at a timing controlled by programming clock pulses (CLK in ) applied to terminal  26 . When programmable crystal oscillator  20  is programmed by the programming data, it produces a clock signal output (F out ) on terminal  26  of a programmed frequency conforming to a customer specification anywhere within a wide range, e.g., 380 KHz to 175 MHz. In accordance with a feature of the present invention described below, oscillator  20  includes a programmable read only memory (PROM)  50 ,  FIG. 2 , into which customer data may be entered as programming data via Program terminal  22  under timing control imposed by clock pulses (CLK in ) applied to terminal  26  by the manufacturer at the time the oscillator is frequency programmed. Thereafter, the customer data may be read out on terminal  25  by applying clock or shift pulses to terminal  21 . If this signature data feature is omitted, the crystal oscillator package configuration illustrated in  FIG. 1  may be reduced to four terminals. 
     Programmable crystal oscillator  20 , illustrated in greater detail by the block diagram of  FIG. 2 , includes a crystal blank  30  electrically connected between pads  31  and  32  on an integrated circuit chip (not shown) for excitation by an oscillator circuit  34  and thus to generate a source (resonant) oscillating signal. This oscillator circuit includes an arrangement of resistor, capacitor, and inverter components well known in the crystal oscillator art and, thus, need not be described here. The frequency of the source oscillating signal, appearing at the output of oscillator circuit  34 , is largely determined by the physical characteristics of the crystal blank  30 . 
     In accordance with a feature of the present invention, programmable crystal oscillator  20  accommodates any crystal blank that oscillates within a wide range of source frequencies. That is, the source frequency may vary from crystal to crystal within a range without jeopardizing the capability of crystal oscillator  20  to be programmed to output clock signals at any frequency specified by a customer within a 380 KHz-175 MHz range, for example. In fact, the diverse crystal source frequencies need not be known in advance. 
     Still referring to  FIG. 2 , oscillator circuit  34  outputs clock signals at a reference frequency F ref , equal to the crystal source frequency, which are applied to a frequency multiplier  36 , illustrated in greater detail in FIG.  3 . The frequency multiplier outputs clock signals at a frequency F pll  to a frequency divider  38 , which divides the frequency F pll  by a programmable parameter N to produce clock signals F out  of a programmed frequency conforming to customer specification. The F out  and F ref  clock signals are applied as separate inputs to a multiplexor  40 . Under the control of program control logic in programming network  42  imposed over line  43 , multiplexor  40  outputs either clock signals F out  or F ref  through an output buffer  44  and onto terminal  26 . As will be described, bringing clock signals F ref  out onto terminal  26  is necessary since this frequency is one of the parameters used to determine how programmable crystal oscillator  20  must be programmed to generate a specified clock signals F out . 
     In accordance with another feature of the present invention, oscillator  20  further includes a pair of load circuits  46  and  48  that may be programmed, if necessary, to adjust the capacitive loading on crystal  30  and, in turn, pull the clock signal frequency F ref  into a range of frequencies conducive to optimal programming of crystal oscillator  20 , as explained in applicants&#39; related application cited above. As described in this application, load circuits  46  and  48  each include an array of discrete capacitors that may be programmed into the crystal output circuit in suitable increments, e.g., five picofarads, under the control of programming network  42  over lines  76  and  86 , respectively. This capacitance loading adjustment is effective to pull the crystal source frequency up or down, as required, to adjust the reference clock signal frequency to a value appropriate for optimal programming of oscillator  20 . Fixed capacitors  75  and  85  provide nominal capacitive loading for crystal wafer  30 . 
     As seen in  FIG. 3 , frequency multiplier  36  includes a frequency divider  52  that divides the reference clock signal frequency F ref  by a programmable parameter Q and applies the resultant clock signal frequency to a phase detector  54  of a phase locked loop (PLL). The phase locked loop also includes a charge pump  56 , a loop filter  60  and a voltage controlled oscillator  58 , that produces the clock signal frequency F pll  going to frequency divider  38  in FIG.  2 . This clock signal frequency F pll  is also fed back through a frequency divider  64  to a second input of phase detector  54 . Divider  64  divides the F pll  frequency by a programmable parameter P. Further details of this phase locked loop are provided in applicants&#39; related application. 
     As described below, the frequency divider parameters Q, P, and N, and, if necessary, adjustments of crystal load circuits  46  and  48 , are programmed via programming circuit  42  by programming data entered through Program terminal  22 . 
     According to another feature of the present invention, the unique qualities of programmable crystal oscillators  20  lend them to being marketed in accordance with a worldwide logistics network illustrated in FIG.  4 . The heart of this network is a centralized order processing center, generally indicated at  70 . Activities supporting the order processing center, but not necessarily undertaken at the order processing center site, are worldwide market forecasting  72  of programmable crystal oscillators  20  demands, which, in turn, drives master production scheduling  74  in terms of package sizes and configurations. Master production scheduling drives manufacturing resource planning (MRP)  76 , that results in a manufacturing plan  78 . 
     In conjunction with worldwide market forecasting  72 , local market forecasting  80  of oscillator demand may also be performed as a basis for master production scheduling  82 . As indicated by transfer link  83 , the master production schedule  74 , based on the worldwide market forecast  72 , is rationalized with the master production schedule  82 , based on numerous local market forecasts  80 , to re-plan the manufacturing plan, which then results in additional manufacturing resource planning (MRP)  84  and a manufacturing plan  86 . Since crystal oscillator demand is extremely dynamic, the manufacturing plan is repeatedly revised (replanned). 
     The production volume of the programmable crystal oscillators  20  in the various package configurations is predicated on the latest manufacturing plan  86 , which is communicated to a production facility or to several geographically dispersed facilities  88 . The crystal oscillators, finished except for programming, testing, and marking, are shipped, as indicated at  89 , to programming centers  90  strategically located to serve market areas throughout the world, as indicated in  FIG. 4 , in volumes determined by a consensus of the worldwide and local market forecasts. The crystal oscillators  20  are placed in inventories convenient to each of the programming center sites where they await customer orders. It is important to note that crystal oscillator production and inventory levels created at various programming center sites are primarily driven by market forecasting and manufacturing planning, not customer orders. 
     As further seen in  FIG. 4 , customers  92  enter crystal oscillator orders into the worldwide logistics network by communicating their orders to agents (sales partners  94 ) located anywhere in the world, using, for example, any one of the illustrated communications links. The orders are relayed to centralized order processing center  70 , again by any available communications link  95 . Each customer order is perused as to quantity and package configuration, and the existing inventory levels at the various programming centers  90  are checked  96  by inquiry over a communications link  97  to a common inventory control facility  98 . The order processing center can then determine which one of the programming centers is best able to fill the customer order, taking into consideration programming center location relative to customer delivery site and inventory level. For a particularly large volume order, two or more programming centers may be designated to fill the order from existing inventory. 
     Each order is processed, as indicated at  100 , and a final schedule  102  is prepared, taking into further consideration the delivery date specified in the customer order. The schedule is communicated as a work order(s) over a communication link  103  to the one or more programming centers  90  designated to fill the customer order by performing the final steps in the manufacture of each crystal oscillator  20 . It will be appreciated that one customer order may specify plural types of oscillators  20  in various quantities, package configurations, signature data, functionalities, and frequencies, etc., with different delivery locations and dates. The order processing center  70  is equipped to readily accommodate any or all of such variables in a customer order. Once the order processing center determines that the customer orders can be filled in all respects, including delivery dates, confirmations of order acceptance are sent back to agents  94  via communications link  105 , who relay the confirmations on to the customers. 
     Upon completion of final production at a programming center, the crystal oscillators  20  are packed and processed  106  for shipment to the customer-specified delivery destination. The common inventory control facility  98  tracks the inventory levels at the various programming centers  90  and so advises manufacturing resource planning  84 . The manufacturing plan  86  is revised to account for inventory depletions on a real time basis, and oscillator production  88  is adjusted accordingly to replenish the programming center inventory to appropriate levels, consistent with up-to-date market forecasts. 
     By virtue of the worldwide logistics network illustrated in  FIG. 4 , a typical leadtime from receipt of customer order at the centralized order processing center  70  to customer shipment of programmed oscillators  20  from programming center(s)  90  may be seventy-two hours or less. Currently, leadtimes in the crystal oscillator worldwide marketplace are measured in terms of weeks and months, not hours. 
     In accordance with a feature of the present invention, each programming center is basically configured in the manner illustrated in FIG.  5 . Programmable crystal oscillators  20 , packaged in industry standard containers (e.g., ESD tubes and tape reels), as received from the production facility  88  (FIG.  4 ), are withdrawn from inventory  108  and loaded as batches of containers  109  at an input  110  of a parts handler  112 . It will be appreciated that mechanical details of parts handier  112  vary depending upon oscillator size and package configuration. Operational control of the parts handler is performed by a commercially available programmable logic controller (PLC)  114  connected to a commercially available, PC compatible computer  116  by a bus  117 . A work order  118 , generated from a customer order, is entered into the computer, either directly as communicated from the centralized order processing center  70  in  FIG. 4 , transcribed by an operator from a work order electronically received from the order processing center and entered manually via a keyboard (not shown), or by a hand held scanner reading a bar-coded work order. To begin filling a work order, computer  116  sends a start signal over bus  117  to PLC  114 , as well as the number of oscillators ordered by the customer. In response to the start signal, the PLC initiates operation of parts handler  112  to remove the programmable crystal oscillators  20  from their containers  109 , one-by-one, and deliver them successively to a program/test position indicated at  120 . Here, the oscillator terminals  21 - 26  are contacted by terminals of a test/program interface board  122  to power, test, and program each programmable crystal oscillator  20 . Interface board  122  may take the form of a test interface board commercially available from PRA, Inc., of Scottsdale, Ariz., that is suitably modified to handle programming inputs to the crystal oscillator, as generated by computer  116 . Such an interface board is already designed to handle oscillator test procedures, such as obtaining output frequency, voltage, current, pulse waveform, and duty cycle readings. These readings are converted to digital data by an analog-to-digital (A/D) converter  124  and input over data bus  125  to computer  116  for comparison against customer specifications, and for programming purposes described below. 
     Upon completion of the test and program procedures, each oscillator  20  is marked with identifying indicia, preferably inscription by a laser beam emitted by a laser  126  as controlled by computer  116  over cable  127 . Depending upon package configuration, laser marking may be performed without moving the programmed oscillator from program/test position  120  or moved to a separate laser marking position by parts handler  112 . If computer  116  determines from the test readings that a particular oscillator fails to meet customer specifications, a fail signal is sent to PLC  114 , which then controls parts handler  112  to deposit the failed oscillator in a reject tray  128 . If desired, the failed oscillator may be laser marked prior to being deposited in the reject tray. 
     Oscillators that pass the test procedure progress to an output  130  of the parts handler  112  where they are re-packed in other industry standard containers  131 . A count of the oscillators is maintained by the PLC as they are packed. As the containers are filled, computer  116  controls a printer  132  over bus  129  to print appropriate identifying labels, which are applied to the containers  131 . The filled containers are packed into shipping cartons (not shown), which are delivered to the customer. 
     It is seen that each programming center  90  is automated to the extent that it may be manned by a single human operator. The only manual operations involved are loading containers  109  filled with programmable oscillators at the input of the parts handler, loading empty containers  131  at the output end of the parts handler, packing filled containers into shipping cartons, applying labels, and, in some cases, computer entry of work orders. 
     The test/programming procedure performed by a programming center  90  on each programmable crystal oscillator  20  when placed in position  120  by parts handler  112  with its terminal connected into interface board  122  ( FIG. 5 ) is illustrated in the flow charts of FIG.  6 . Interface board  122  of  FIG. 5  is equipped with a regulated power supply to selectively apply, as controlled by computer  116 , an adjustable supply voltage V DD  to oscillator terminal  24  and V ss  (ground) to oscillator terminal  23 , to thus power up the oscillator. 
     As illustrated in  FIG. 6 , the test/program procedure is initialized in step  140 , and the programmable crystal oscillator  20  electrically connected into interface board  122  is powered up in step  142 . Computer  116  conditions multiplexor  40  via the program control logic in program network  42  to route reference clock signals F ref  to the F out /CLK in  terminal as seen in  FIG. 2 , and a reading (step  144 ) of the F ref  frequency is taken, converted to digital data by A/D converter  124  and fed to computer  116  (FIG.  5 ). 
     In step  146 , the computer determines optimal values for the P, Q, and N divider parameters by calculation based on the formula F T =F ref ·P/(N·Q), where F T =customer-specified target frequency, and F ref =reading from step  144 . 
     As indicated in applicants&#39; cited application, it is advantageous that the Q parameter of divider  52  be programmed to achieve a condition where F ref /Q clock signal frequency applied to one input of phase detector  54  in the phase locked loop circuit of  FIG. 3  is in the range of 32 KHz-50 KHz (preferably 42.395 KHz-43.059 KHz). This means that the P parameter of divider  64  must be programmed to a value, such that the F pll /P clock signal frequency output by counter  64  to the other input of phase detector  54  is equal to the F ref /Q clock signal frequency to achieve stable phase loop locked circuit operation. However, the programmed P value and the value of N for divider  38  (FIG.  2 ), are factors in achieving the target frequency specified by the customer, as seen from the above equation. 
     In accordance with industry practice, every output frequency F out  specified by a customer order is stated in terms of a target frequency F T  plus/minus an acceptable accuracy expressed in ppm (parts per million). The industry standard frequency accuracy for crystal oscillators is 100 ppm, which is ±0.01% of the target frequency F T . 
     While the range of each of the programmable parameters Q, P, and N is provided in the dividers to achieve a F ref /Q frequency within the preferred range of 42.395-43.059 KHz and to achieve an F out  frequency close to the customer&#39;s F T  frequency, the programmed F out  signal may not achieve the ppm customer specification, because P, Q and N are typically integers, and the factor P/QN therefore may not yield the specified output frequency accuracy. Thus the objective sought by the computer in step  146  is to determine an optimal combination of P, Q, and N values that meets or beats the customer&#39;s ppm specification. Thus, the computer calculates an F out  frequency using the determined optimal combination of P, Q, and N values according to the above equation, and then determines in step  148 , whether the calculated F out  frequency satisfies the customer&#39;s ppm specification. If it does (yes), the computer then executes step  150 . In this step, programming data bits representing the determined optimal P, Q, and N divider parameters are assembled by the computer into a programming word in step  150 . An example of this programming word is illustrated in FIG.  7 . This programming word is entered via the Program terminal into the register and stored in the PROM of programming network  42  ( FIG. 2 ) in step  152 . This step is accomplished by shifting the programming work into the programming network register via the Program terminal  22  by the application of the appropriate number of shift pulses to the F out /CLK in  terminal  26 . 
     Now that the programming word has been entered into the programming network register to complete step  152 , it is then non-volatilely stored in the programmable read only memory (PROM) of the program network  42  of FIG.  2 . This PROM may take the form of an array of fuses, which are selectively blown under the control of the programming word held in the shift register and the program logic included in the program network  42 . To this end, and in accordance with the current embodiment of the present invention, the Program terminal is held low and the V DD  voltage is raised to a high level, while clock pulses are applied to the F out /CLK in  terminal. In response to the successive clock pulses, the data bits of the programming word residing in the shift register are serially stored in the PROM either by blowing or not blowing fuses. With the completion of step  152 , oscillator  20  should now be programmed to generate clock signals on its terminal F out /CLK in  of a frequency conforming to customer specifications of target frequency F T  and ppm. 
     In the next step  154 , customer-specified data is assembled into a signature word. The signature data word includes any information a customer wishes to store in PROM  50  that may be unique to each programmable crystal oscillator  20 , such as an auto-incremented ID number, traveler information for trouble-shooting and QC tracking purposes, etc. The assembled signature word is stored (step  156 ) in the same manner as the frequency programming word in step  152 , i.e., entered bit-by-bit into the programming network register via Program terminal  22  by clock pulses CLK in  applied to terminal  26  and then clocked out of this register into PROM  50  by an additional string of clock pulses CLK in  generated by computer  116 . 
     Now that the programming and signature words have been stored in their respective PROMs, which in practice may be separate areas of a single PROM, the next step is to verify that the now programmed crystal oscillator  20  does generate an output frequency conforming to the customer specification ppm. Multiplexor  40  in  FIG. 2  is conditioned to route the output of divider  38  to the F out /CLK in  terminal  26 , and the programmed frequency of the oscillator ouput clock signals F out  and other parameters are read in step  158 . Such other parameters include voltage, current, pulse waveform and duty cycle. Once the output clock signals are read, the programmed crystal oscillator  20  is powered down (step  160 ). If the computer determines in step  162  that the programmed oscillator signal ppm and parameters indeed satisfy customer specifications in all respects, the crystal oscillator  20  is accepted (step  164 ), whereupon it is laser marked and then packed by parts handler  112  of  FIG. 5  into a container  131  at the output end of the parts handler. If not, the oscillator is rejected (step  166 ), whereupon it is directed to reject tray  128  by the parts handler. As soon as the reading is taken in step  160 , the programmed oscillator is replaced by the parts handler with the programmable oscillator next in line. 
     If step  148  determines the customer&#39;s ppm specification is not met by the computer&#39;s F out  frequency calculation in step  146 , it is then necessary to pull the crystal oscillation frequency, (and also the F ref  frequency), in the requisite up or down direction by appropriate programming of load circuits  46  and  48  in FIG.  2 . To this end, the computer executes step  170 , indicated in FIG.  6 . According to this step, the computer determines, such as by reference to a lookup table (LUT), what available load circuit adjustment would be effective to pull the F ref  frequency (and thus the F ref /Q frequency) to a predicted value that will fine tune F out  to a frequency that satisfies the customer&#39;s ppm specification. A description of how the programmed adjustments of load circuits  46  and  48  are accomplished is provided in applicants&#39; related application. Step  146  of calculating the P, Q, and N values is then repeated for the pulled (adjusted) F ref  frequency prediction, and the recalculated F out  frequency is tested in step  148  against the customer&#39;s ppm specification. If the specification is now met, the sequence of steps  150 ,  152 ,  154 , etc., described above, are then executed. However, in step  150 , crystal pull programming bits  117  for programming load circuits  46  and  48  are assembled into the programming word illustrated in FIG.  7 . 
     If characteristics of crystal blanks  30  have not been tested beforehand, and thus are of unknown quality, it cannot be predicted what pulling effects programmed adjustments of the crystal load circuits will have on the F ref  frequency. In this case, if ppm is not met in step  148 , it may be desirable to perform subroutine  173 , wherein, step  174  is executed in the same manner as step  170  to determine the extent to which the frequency F ref  should be pulled. The computer then calculates in step  176 , optimal P, Q, and N parameters based on the predicted F ref  frequency, as pulled (adjusted), and assembles a programming test word (step  178 ) including the data bits of the P, Q, and N values determined in step  176  and the crystal pull data bits determined in step  174 . This programming test word is entered in step  180 , and the F out  frequency is read (step  182 ) and tested to see whether it meets the customer ppm specification in step  184 . If it does, the computer converts the programming test word assembled in step  178  into an assembled programming word in step  150 . Steps  152 ,  154 ,  156 , etc., are then executed, as described above. 
     If step  184  determines the customer&#39;s ppm specification is not met, step  174  is performed again to determine different crystal pull data bits that modify the load circuit adjustment and recalculate optimal P, Q, and N values (step  176 ). A new programming test word is assembled in  178 , entered in step  180 , and the F out  frequency is read (step  182 ) and tested against the customer&#39;s ppm specification in step  184 . This subroutine may be repeated several times until the F out  frequency meets customer specification (step  184 ). Only then is a programming word stored in PROM by complete execution of step  156 . 
     From the foregoing description it is seen that the present invention provides a dramatically improved method for marketing crystal oscillators to customer specification. By virtue of the crystal oscillators being frequency programmable, crystal manufacture can be economized and expedited, since the necessity of processing the crystal wafers to oscillate at specific frequencies is relaxed to the point where they need only oscillate at frequencies with a wide range of frequencies. Thus, manufacturing steps, such as etching, intermediate and fine lappings, and selective plating of the crystal wafers to specified frequencies, testing and sorting, may be reduced in duration, simplified, or even eliminated. In fact, by virtue of the present invention, crystal oscillators, manufactured to customer specification prior to cancellation or delivered to a customer and subsequently unneeded because of market conditions, need not be scrapped completely, since, in many cases, at least the crystals can be re-manufactured into programmable crystal oscillators  20 . 
     In terms of customer benefits, a major advantage of the present invention is the elimination of long leadtime. Customers, faced with long leadtimes, may be forced to spread orders among multiple manufacturers, suffer delays in new product introductions, face inabilities to meet product demand, and/or resort to high inventory buffers at manufacturing sites or customer sites. If new product introductions are delayed or abandoned or forecasted market acceptance fails to materialize, customers may be subjected to contractual penalty charges, supply rescheduling or order cancellations. In contrast, short leadtimes afforded by the present invention allow customers to match their production to actual market demand, take advantage of “just in time” inventory control, and reduce liability to manufacturers for material, work in progress, and finished goods prior to delivery. 
     It will be readily appreciated by those skilled in the electronics art that, while the foregoing description has been directed to programmable crystal oscillators, the principles of the present invention may be utilized in the manufacture and distribution of other types of electronically programmable devices, such as programmable logic arrays, programmable gate arrays, programmable timing generators, programmable analog arrays, etc. Also, the present invention is clearly applicable to programmable crystal oscillators that are temperature-compensated (TCXOs) and voltage-controlled (VCXOs). 
     While the present invention has been described in the context of using a standard microprocessor-type crystal blank that oscillates in the range of 5.6396 MHz to 27.3010 MHz, as noted above, it will be understood that the present invention may be achieved using an industry standard watch crystal mass produced to oscillate at 32.768 KHz. In this case, the desired low phase-locked loop frequency may be achieved without the need for frequency divider  52  in frequency multiplier  36  of FIG.  3 . Crystal blank  30  would then, in effect, be coupled in direct drive relation with the phase-locked loop circuit. Since watch crystals, by virtue of mass production, are significantly less expensive than microprocessor-type crystals, further economies in the production of programmable crystal oscillators in accordance with the present invention may be achieved. 
     It will be apparent to those skilled in the art that various modifications and variations may be made to the worldwide marketing logistics network of the present invention without departing from the spirit of the invention. Thus, it is intended that the scope of the present invention cover modifications and variations thereof, provided they come within the spirit of the appended claims and thus equivalents. 
     Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.