Method and apparatus for controlling tape transport apparatus for cassettes

#The present invention relates to improvements in methods and apparatus for transferring a flexible web from reel to reel of a web/reel assembly, and more particularly to tape transport apparatus for tape cassettes and methods for controlling and operating such apparatus. In more detail, the present invention relates to improvements in the method and apparatus disclosed in the commonly assigned prior application Ser. No. 810,276 filed June 27, 1977, now U.S. Pat. No. 4,172,231, which describes methods and apparatus for accurately determining absolute values of the tape position as tape is driven from reel to reel of a tape/reel assembly, and for controlling the apparatus in accordance with such tape position determinations.

#The invention of the aforesaid prior application is described therein as useful in transport apparatus for reel/web assemblies the physical parameters of which are known, the physical parameters including the tape length and thickness, and the reel hub diameters. In such a transport apparatus operating with a web/reel assembly having known physical parameters, the position relative to one end of the web of an intermediate portion being transferred from one reel to the other, may be determined by a computational process using mathematical equations, i.e. by following tape position determination algorithms employing constants established by the known physical parameters of that reel/web assembly, and a variable parameter; namely, the ratio of rotational speeds of the two reels as the intermediate web portion is being transferred from one reel to the other, which ratio continuously changes as the web is transferred. It is explained in said prior application that the same algorithms employing the same constants may be followed to determine the position of an intermediate web portion at any stage of transfer of the web; the only input required at any stage is the ratio of the rotational speeds of the reels. By determining tape position in a regularly repeating cycle, using said tape position determination algorithms, and producing each cycle an output signal representing the position determined for the web during that cycle, the output signals may be utilized to monitor the transfer of the web in the apparatus, for example, by displaying the continuously changing position of the web or controlling the operation of the transport apparatus.

#The method of said prior application is particularly, although not exclusively, useful in tape transport apparatus for cassettes of tape which are a standard type for example, cassettes providing sixty, ninety and one hundred twenty minutes of playing time known, respectively, as C-60, C-90 and C-120 cassettes. Such cassettes are conventional with two reels and different known lengths and thickness of tape to provide the various lengths of playing time. The method entails first establishing constants for each tape cassette, which constants are used in the position determination algorithms, and storing a set of constants for each tape cassette in, for example, a semiconductor memory unit. In tape transport apparatus under the control of a microprocessor, signals respresenting the set of constants corresponding to the cassette loaded into the transport apparatus, are recalled from the memory unit, intermediate signals are generated representing the ratio P.sub.1 /P.sub.2 measuring the rotational speeds of the reels, and by circuit means such as the microprocessor under program control a determination is made of tape position in terms of the length (l.sub.1 or l.sub.2 ) or time (t.sub.1 or t.sub.2) to the end of the web on either reel of an intermediate portion of the web being transferred from one reel to the other, using position determination algorithms employing the following equations: ##EQU1## L representing the total length of magnetic tape, l.sub.1 representing the used tape, l.sub.2 the unused tape, T representing the ratio P.sub.1 /P.sub.2 when L=l.sub.2, i.e. at the beginning of the tape. T is thus a constant which characterizes each type of cassette and which can be determined either mathematically or by experiment.

#Further objects and features of the invention will be apparent from the following description of a preferred embodiment of the invention, by reference to the accompanying drawings, in which:

#FIG. 1 is a block diagram of a tape transport apparatus including a controller of the apparatus instructed in accordance with the present invention;

#FIG. 2 is a block diagram similar to FIG. 1, detailing the memory sections of the controller and diagrammatically illustrating the controller output to the display and motor control circuit for the reel drive motors of the tape transport apparatus;

#Now turning to the drawings, FIGS. 1 and 2 are block diagrams of tape transport apparatus having a control system constructed in accordance with the present invention and utilizing the methods of the present invention. The system, in general, includes a controller 36, a motor control circuit for the drive motors of the tape transport apparatus, a display for monitoring tape movement by visually displaying tape position, an operator panel with a key board and control switches, and reel speed detectors herein shown as pulse generators supplying information on reel speed to the controller 36. In the preferred form of the invention the controller 36 is comprised of a set of integrated circuit chips forming a microprocessor, an exemplary and preferred microprocessor being the Mostek F8 which includes a CPU unit 38 and one or more ROM memory units 40. As indicated in FIG. 2, the controller 36 includes a timer 42, which in the case of the Mostek F8 microprocessor is provided by the memory unit 40, and has an external reference frequency input 44 which provides a time base so that the timer is operable in real time.

#While it is preferred to utilize a Mostek F8 family of chips to provide a microprocessor based controller 36, it will be appreciated that other microprocessors are available and may be used to serve the same functions, and that the controller may be implemented using other equivalent electronic devices. While implemented with the Mostek F8 chips, the F8 CPU provides 64 bytes of RAM that may serve various register functions unique to the present invention, as well as provide read/write memory for arithmetic and logic functions. The CPU among other circuits also includes an arithmetic logic unit, an accumulator, I/O ports, clock circuits, and interrupt logic which allows CPU operation to be interrupted by a timer on the ROM chip or by an external source. One or more F8 ROM chips provide for storage of programs, I/O ports, a timer and program counter and stack register which handle the program function. With this construction, direct interfaces can be made by the controller 36 with peripheral devices since the CPU circuits provide, for example, encoding and decoding circuits for operating a display. The ROM's also provide for storage in coded signal form of the various unique constants required for cassette identification, search for target positions and other tape control functions performed by the apparatus, labeled in FIG. 2 as memory sections or blocks Cassette I.D. Store, Cassette Constants Store and Reel Pulse Count Store.

#Operator activated inputs to the controller 36 are provided from an operator panel having one keyboard for digit keys 0-9, a cassette identification mode key 48 labeled "I.D." and cassette keys 50 labeled, C-45, C-60, C-90 and C-120, and a second keyboard with function keys 52 labeled play, record, stop, etc. which also includes the search mode key 54.