WO1989000503A1

WO1989000503A1 - Control of printer functions via band id

Info

Publication number: WO1989000503A1
Application number: PCT/US1988/002505
Authority: WO
Inventors: Richard J. Stilwell, Jr.
Original assignee: Storage Technology Corporation
Priority date: 1987-07-21
Filing date: 1988-07-21
Publication date: 1989-01-26

Abstract

A method and apparatus for controlling the functions of high-speed line printers (10) through use of a preselected portion of a band identification mark (26) indicative of the function to be controlled. The rotating band (12), with its encoded band identification mark (26) is read by a band sensor (28) in order to determine whether the band identification mark (26) corresponds to a value stored in a look-up table. If the band identification mark (26) compares favorably with a stored value, a machine co-processor (34), through a system bus (42), commands the band speed to be set in conformance with the encoded band identification mark (26).

Description

CONTROL OF PRINTER FUNCTIONS VIA BAND ID

Background of the Invention

This invention relates generally to high-speed line printers, and more particularly to a method and apparatus for controlling the functions of such printers through use of a band identification (ID) mark.

As is well known, high-speed line printers typically comprise a flexible, endless print band supported by spaced-apart drive pulleys adjacent one or more rows of uniformly-spaced print hammers along a print line. For example, in the Impact 5000 Series high-speed line printers manufactured by Documation Incorporated, (now StorageTek Printer Corporation) a subsidiary of Storage Technology Corporation, band drive has been achieved through use of a brushless DC motor housed within one of the band pulleys. Band tension, on the other hand, is achieved by a spring-loaded idler pulley that permits the operator to easily change print bands. However, the direct drive nature of the brushless DC motor housed within the band pulley, as well as conventional microprocessor control, permits band speed changes without the need for belt and pulley changes commonly associated with such. In this manner, the print band is rotated at a substantially constant speed depending on the desired printing speed relative to the row or rows of print hammers.

There are typically two kinds of timing marks on the print band: (1) character marks; and (2) intermediate marks. Such marks are distinguishable only by their physical position relative to the other timing marks and characters on the print band. The character marks occur once per character, while the intermediate marks appear centered between character marks most often appearing (in the case of the Impact 5000 Series printer) before one of the first 16 character marks. As is conventional, the intermediate mark preceding the first character mark identifies the home position of the band.

In order to print correctly, some means of printing control must operate in synchronism with the moving timing marks. That is, the signals generated by print position circuitry must agree with the timing marks as they are moving toward alignment with the print hammers selected to be actuated. One means for achieving synchronization of the print controls employs a reference transducer means which generates a home or reference signal when a reference character, such as the home position character mark described hereinabove, is at a predetermined location relative to a given print hammer. The reference transducer means generates the reference signal by sensing one or more reference marks indicative of the reference character and movable with the timing marks.

The means for achieving synchronization usually employs synchronization control circuitry activated by the reference signal which counts timing signals between reference signals and at reference signal time generates a synchronization control signal which is used to actuate the print controls to initiate printing. Thereafter, the synchronization control circuitry operates at reference signal times for determining whether the print position circuitry is generating a reference character signal. In the event the print position circuitry is not generating a reference character signal at reference pulse time, a synchronization control pulse is generated for use to discontinue printing and/or to indicate an error appearing. With such an arrangement, as noted in U.S. Patent No. 4,425,844, issued to Carrington et al, and assigned to International Business Machines Corporation, changing type speeds to enable the printer to be operated at plural different printing speeds presents a problem. This is simply because of the fact that different lead distances are required for different type speeds where the flight time of the given hammer remains the same. One option suggested therein for accomplishing lead distance change might be to physically change the position of the reference transducer. Another option is to change the position of the reference mark relative to the reference character. A third might be to provide multiple reference marks located at different distances relative to the reference character. A fourth option might be to replace the control circuitry to function for different reference characters. Each of the above- mentioned options, Carrington et al further note, have serious drawbacks such as increased cost, structural complexity and opportunity for error upon operator intervention. Furthermore, none of the above-mentioned options allow complete flexibility in the choice of speeds due to the fact that the lead distance for certain speeds is at a position which is not equal to an integer number of timing or emitter marks. As a result, Carrington et al disclose electronic means for compensating for changes in the lead distances for different character speeds, such means changing the timing of the reference pulse which is always generated for all speeds when the reference character is at a fixed lead distance from the given print hammer.

One other prior art approach in which the print speed of a band printer may be selectively controlled is disclosed in U.S. Patent No. 4,649,501 issued to Bloom et al, and assigned to International Business Machines Corporation. As taught therein, a printer control system uses two microprocessors and a print control for operating a plurality of print hammers in synchronism with a revolving type character band such as the aforedescribed print band. One microprocessor is a mechanical control processor, and the other microprocessor is a print control processor that communicates with a host system for receiving print and control data used by the print control and the mechanical control processor for operating the printer. The mechanical control processor monitors a speed selection device such as an operator panel with speed control keys, and operates controls for operating drive means for moving the type carrier at selected speeds. On the other hand, the print control processor supplies speed control data from a diskette to the mechanical control processor for control of the type carrier speed. It is readily apparent from the above that selection and control of band speed in conventional high-speed line printers may be accomplished in one of two ways: either (1) by mechanically adjusting the component parts of such printers in order to synchronize the timing marks at varying speeds; or (2) by incorporating significant hardware and software changes in order to selectively control the band speed through a plurality of microprocessors responsive to operator commands. It would, therefore, be desirable to provide a means for controlling the functions of a high-speed line printer without operator intervention.

Summary of the Invention

Accordingly, it is a general object of the present invention to provide a method and apparatus for controlling the functions of a high-speed line printer. More specifically, it is an object of the present invention to provide a method and apparatus for control of such printer functions without operator intervention.

Another object of the present invention is to eliminate "character ghosting" through incorporation of the above-desired method and apparatus.

Briefly, these and other objects of the present invention are accomplished through indicator means which are linked to the band identification (ID) via system software. Upon recognition of the indicator means by the system microcode, various printer functions may be changed regardless of the functions selected at the printer operator-panel, or commands from the host. In those cases where the indicator means is not present in software, the printer will return to the selected or commanded function automatically. These and other objects, advantages, and novel features will become more apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 diagrammatically illustrates the component parts of a high-speed line printer having a flexible print band;

Fig. 2 shows an enlarged portion of the print band illustrated in Fig. 1; Fig. 3 illustrates in block diagram format a printer controller according to the present invention, including a machine co-processor (MCP) ;

Fig. 4 shows a block diagram of the MCP illustrated in Fig. 3. Fig. 5 illustrates schematically one means for regulating band speed according to the present invention; and

Fig. 6 is a flow diagram for controlling printer functions according to the present invention.

Detailed Description of the Invention

Referring now to the drawings, wherein like characters designate like or corresponding parts throughout the several views, there is shown in Fig. 1 a portion of a high-speed line printer 10 including a print or character band 12 rotatable in the direction of the arrow as shown by means for driving (not shown) a pair of pulleys 14. The character band 12, which is located directly in front of a plurality of print hammers 16, rotates at a substantially constant speed. In this manner, the characters on the band are successively presented to each hammer 16. As will be described in greater detail hereinbelow, when a given hammer 16 is selected for printing, the hammer 16 drives the forms 20 and towel ribbon 22 against the raised character on the character band 12 and platen 18. The character band 12, as shown more clearly in Fig. 2, includes two kinds of timing marks which are distinguishable only by their physical position relative to the other timing marks and characters on the band. A plurality of character marks 23 appear on the character band 12, one such character mark 23 beneath each pair of characters 24, while intermediate marks 26 appear centered between the character marks 23. In those character bands 12 which are utilized in a line of printers known as the Impact 5000 Series high-speed line printers manufactured by Documation Incorporated, the intermediate marks 26 only appear before one of the first sixteen character marks 23. As is conventional, the intermediate mark 26b preceding the first character mark 23a identifies the home position of the band 12. The presence or absence of an intermediate mark 26 before each of the first sixteen character marks 23 is detected in a conventional manner by a band sensor 28 (Fig. 5) as a string of sixteen bits. These sixteen bits read from the character band 12 constitute framing bits and band ID bits. As shown in Fig. 2, the first two bits are the start pattern 1-1, while the last two bits are the stop pattern 0-1. Between the start pattern and stop pattern, the intervening twelve bits are interpreted as a twelve-bit binary integer ranging from 0-4095 in decimal value, with the most significant bit (MSB) detected first. In such a manner, the framing bits permit unambiguous detection of the home position. Printer control is typically provided by a printer controller 30 as shown in Fig. 3. The printer controller 30 is comprised generally of: an interface co-processor (ICP) 32; a machine co-processor (MCP) 34; upper and lower hammer control processors (HCP) 36a and 36b; plus a shared storage memory 38 and a dual floppy drive assembly 40. Communications between the ICP 32, the MCP 34, HCP 36a, 36b, shared storage memory 38, and dual floppy drive assembly 40 is accomplished through a system bus 42. Further details relating to the operation and control of the Impact 5000 Series printers may be found in the following Documation Incorporated manuals, each of which are incorporated herein by reference: "Theory of Operation" - 3800014155; "Product Description Manual" - EP-026-0; "Operator's Manual" - 3800014171; "Maintenance Manual"-3800014131; "Interface Feature Manual" - 3800014159; "Installation Manual" - 3800014151; "Illustrated Parts Catalog" - 3800014141; and "Schematics" - 3800014161.

Referring now to Fig. 4, operation of the MCP 34 will now be described. The MCP functions as the interfacing and coordinating processor between the ICP 32 and the significant printer functions. For example, the MCP 34 is responsible for execution of commands resident in the command stack (not shown) . It determines which hammer bank should be used and assigns each command accordingly, as well as prepares a print schedule for assignment of print lines to the appropriate HCP 36a or 36b. It also directs forms advancing by informing a forms advance system (not shown) through, for example, a forms stacker interface 43, the number of lines to move in order to keep the form properly aligned with the print data. The MCP 34 also directs, through a band interface 44, the band motor when to start and stop the print band 12. Other functions, not germane to the present invention, are shown in Fig. 4 and described in greater detail within the above-referenced Documation Incorporated publications. Control of the character band 12 typically consists of controlling the speed of the band 12 by turning the band motor on and off, insuring that printing does not occur when the band speed is out of the allowable tolerances, keeping track of the position of the band to the character clock level, detecting the band index mark or home position, and checking that such detection occurs at the right character clock, reading the band ID from the band 12, controlling the height of the band 12 and detecting when the band 12 is mounted upside down. Referring now to Fig. 5, there is shown a schematic diagram of the circuitry required for band speed regulation according to the present invention. The band sensor 28 measures and controls timing of the character band 12. Character clock (CC) and band ID or identification information are interlaced on the band 12. When the character band 12 is running, the first negative transition from the band sensor 28 clocks an interrupt flip-flop 46. One side of the interrupt flip- flop 46 interrupts the MPU (Fig. 4) while the other side loads a start count into a counter timer chip, the counter value into a hold register and the start count into the counter of the programmable timer module shown in Fig. 4. When the MPU (Fig. 4) senses a band interrupt, it acknowledges the interrupt and resets the interrupt flip-flop 46. Software in the interrupt handler (Fig. 4) reads the value of the hold register to determine the band speed. Thereafter, the band is turned on in a forward direction until the goal speed is reached, whereupon regulation of the speed is controlled by turning the band motor on and off as required. At high band speeds, such interrupts will occur approximately every 246 microseconds while the band index pulse occurs at 123 microsecond intervals during band index sensing. Along with the speed control of the band 12, a voltage controlled oscillator (VCO) 48 is used to generate a 96 CC signal. Such signal, in effect, is a 246 microsecond time span divided by 96. It should be noted at this juncture that each 246 microsecond time span is substantially equal to 0.120 inches (i.e., the distance between character marks 23) of band travel at high band speed. An index signal that restarts the HCP 36a, 36b, 96 CC counters is generated every revolution of the band 12.

The VCO 48 synchronizes its output frequency, divided by the 96 CC signal to the band clock. Accordingly, such circuitry must filter out the band ID information because the ID signal arrives at the band frequency times two, thereby causing a jump in the frequency of the VCO 48. However, when the band 12 is coming up to speed, it must be tracked by the VCO 48. As a result, the VCO 48 is permitted to look at all band CC and ID signals until the band speed is regulated. Thereafter, the VCO lock bit is dropped and the band ID signal to the VCO 48 is filtered out by a ID filter 50. As discussed hereinabove with reference to Fig. 2, the presence or absence of an intermediate mark 26 before each of the first sixteen character marks 23 is detected in a conventional manner by a band sensor 28 as a string of sixteen bits. These sixteen bits read from the character band 12 constitute framing bits, including a two-bit start pattern 1-1 and a two-bit stop pattern 0-1, as well as twelve band ID bits. The intervening twelve bits constituting the band ID are interpreted by the machine co-processor (MCP) 34 as a twelve-bit binary integer ranging from 0-4095 in decimal value. For example, the band ID shown in Fig. 2 is read by the band sensor 28 as "CO 11" (base 16) . However, in order to control various functions of the printer 10 through use of the band ID mark, an indicator means contained, for example, in software present on the disk contained in the floppy drive assembly 40 (Fig. 3) may be used to designate various functions.

For example, in certain applications for high¬ speed line printers which use heavy or multipart forms, the character adjacent to the current printing position will image due to the stress of the ribbon/paper interface around the edge of the adjacent character etching on the band 12. This phenomena is commonly referred to in the art as "ghosting". Such ghosting may occur, for example, in the Impact 5000 Series printers manufactured by Documation Incorporated, when using a 0.120 inch pitch character band 12 at a band speed of 215 inches per second. In accordance with one important aspect of this invention, the ghosting experienced in such printers may be minimized by removal of every other character 24 on the character band 12 (i.e., making it a 0.240 inch pitch band) and increasing the band speed to approximately 305 inches per second with both hammer banks enabled. Such a unique method, with its concomitant increase in speed, may be accomplished by utilizing the band ID bits to designate the requirement for the increased band speed. As such, upon reading of the band ID (including the preselected portion thereof contained in the floppy drive assembly 40 constituting a means for indicating the band speed) the band speed will be automatically set to 305 inches per second regardless of the speed selected at the printer-operator panel or from the host computer. In those cases where the requirements for such a unique band has been removed, the printer 10 will return to the selected speed automatically.

Referring now to Fig. 6, a method of selecting band speed in a high-speed line printer will now be illustrated. It should be noted at this juncture that the flow diagram illustrated in Fig. 6 may be stored algorithmically in the machine co-processor (MCP) 34. The algorithm is commenced at step 100 whereafter a determination is made of whether the character band is rotating at step 102. If the character band 12 is not rotating, rotation thereof is commenced at step 104 after which the band ID is read by the band sensor 28 at step 106. A check is made at step 108 at a look-up table, such as the directory of the disk stored within the dual floppy drive assembly 40 (Fig. 3) , where values of a plurality of band ID bits corresponding to selected band speeds, or other such printer functions controlled by the indicator means, is stored. Thereafter, a determination is made of whether the band ID read from the rotating character band 12 compares to one of the stored values in the look-up table at step 110. If the read band ID does not compare to one of the stored values, an error signal is generated and no printing is attempted. Otherwise, at step 114, a check is made of the file contained in the floppy drive assembly 40 disk to determine if it contains speed control information. If the file contains such information, the machine co- processor (MCP) 34 sets the speed of the character band 12 in accordance with the indicator means. Otherwise, the band speed is set as selected at the operator's panel or host.

Obviously, many modifications and variations of the present invention are possible in light of the above teachings. For example, other printer functions may be equally encoded within the indicator means and their corresponding values stored in look-up tables in order to permit control of the printer without operator intervention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Claims

What is Claimed is:

1. In a high-speed line printer having a plurality of characters movable in a closed path upon a flexible, endless band, a plurality of print hammers electrically operable through control means, and a memory for engaging the characters upon the band at print positions along the path to effect printing of such characters on a print medium, apparatus for changing the speed of the band comprising: drive means for rotating the band at a plurality of selected speeds; means for indicating which one or more of said plurality of selected speeds is appropriate for proper operation of the band, said indicating means including data corresponding to appropriate speeds for each of a plurality of different bands; band identification means imprinted upon the band, said band identification means uniquely corresponding to a portion of said data in said indicating means which corresponds to the band; means for sensing said band identification means; and processor means, coupled between said drive means and said sensing means, for controlling said drive means in response to said indicating means.

2. The apparatus according to claim 1, wherein said band identification means comprises a plurality of timing marks embossed upon the band.

3. The apparatus according to claim 2, wherein said timing marks comprise a plurality of character marks centered beneath respective characters upon the band, and a plurality of intermediate marks between selected ones of said character marks.

4. The apparatus according to claim 3, wherein said band identification means comprises: a home position mark comprising a selected one of said intermediate marks; framing bits including a start pattern following said home position mark and a stop pattern; and a selected plurality of band identification bits between said start pattern and said stop pattern; wherein each said framing bit and band identification bit is indicated by the presence or absence of a respective intermediate mark.

5. The apparatus according to claim 4, wherein said indicating means comprises a preselected portion of the memory, said preselected portion of memory having data corresponding to a plurality of band speeds each of which are uniquely associated in said memory to one or more different bands.

6. Apparatus for controlling selectable functions of a high-speed line printer having a memory, a plurality of characters movable in a closed path upon a flexible, endless band, a plurality of print hammers disposed in a pair of hammer banks parallel to the path and electrically operable for engaging the characters upon the band at print positions along the path to effect a dual-line printing of such characters on a print medium through a towel ribbon, comprising: drive means for rotating the band; means for indicating which one or more of said selectable functions is appropriate for proper operation of the band, said indicating means including data corresponding to appropriate functions for each of a plurality of different bands; band identification means imprinted upon the band, said band identification means uniquely corresponding to a portion of said data in said indicating means which corresponds to the band; means for sensing said band identification means; and processor means, coupled to said drive means and said sensing means, for controlling said drive means in response to said indicating means.

7. The apparatus according to claim 6, wherein said band identification means comprises a plurality of timing marks embossed upon the band.

8. The apparatus according to claim 7, wherein said timing marks comprise a plurality of character marks centered beneath respective characters upon the band, and a plurality of intermediate marks between selected ones of said character marks.

9. The apparatus according to claim 8, wherein said band identification means comprises: a home position mark comprising a selected one of said intermediate marks; framing bits including a start pattern following said home position mark and a stop pattern; and a selected plurality of band identification bits between said start pattern and said stop pattern; wherein each said framing bit and band identification bit is indicated by the presence or absence of a respective intermediate mark.

10. The apparatus according to claim 9, wherein said indicating means comprises a preselected portion of the memory.

11. The apparatus according to claim 10, wherein said indicating means further comprises: a first plurality of bits within said preselected portion, said first plurality of bits being indicative of a selected band speed; and a second plurality of bits within said preselected portion, said second plurality of bits being indicative of at least two selected modes of operating the pair of hammer banks, wherein one of said at least two selected modes enables both of the hammer banks while another of said at least two selected modes enables only one of the pair of hammer banks.

12. A method of selecting band speed in a high¬ speed line printer having a plurality of characters movable in a closed path upoiv a flexible, endless band, and a plurality of print hammers electrically operable for engaging the characters upon the band at print positions along the path to effect printing of such characters on a print medium, wherein the method comprises the steps of: providing the band with sensible band identification means, said band identification means including indicating means corresponding to one or more band speeds that are uniquely appropriate to a given band; storing a plurality of band speeds together with a plurality of band identification means in memory means, each said stored speed corresponding both to each said unique speed for a respective one of a plurality of different bands, and to a respective one of said stored ^• plurality of band identification means; rotating the band with drive means, said drive means being adapted to rotate the band at each of said stored speeds; reading said band identification means, provided upon the band, during rotation of the band by said drive means; comparing said read band identification means with said stored plurality of band identification means; determining from said memory means said stored speed that corresponds to said read band identification means; and controlling said drive means to maintain the rotation of the band at said stored speed that corresponds to said read band identification means.