Signal Generating Device Including Programmable Counters and a Programmable Serial Bit Pattern Generator

The invention relates to a microprocessor comprising registered counting means that have a clock input for under control of attainment of a predetermined clock count generating a command signal on a command signal output thereof. Various counting means have been described for use in a microprocessor, such as U.S. Ser. No. 07/048,841, filed May 1, 1987, now issued in U.S. Pat. No. -4,792,892. The reference relates to a microprocessor, wherein a program loop instruction has a delay field. Through this delay field, the actual start of the loop is delayed over a specified number of intervening instructions. After attaining the first loop instruction, both the number of instructions within a single execution of the loop and the number of successive executions of the loop are counted for so attaining a correct execution of the program. The present invention is not directed, however, to counting instructions.

A particularly interesting microprocessor architecture has been devised for the so-called SPARC processor, of which various features have been presented in the earlier, non-prepublished application U.S. Ser. No. 07/896,062, now issued U.S. Pat. No. 5,659,797 corresponding to EP 91 201 610.2; EP 92 201 737.1 to the same applicant, herein incorporated by reference. The present invention has recognized that a single microprocessor design, such as according to the second reference, but not limited thereto, could be amended for and/or directly run under various different clock pulse frequencies, retaining however the need for invariant execution of the intended program. This would represent a need for using programmable delays and recurrence times. Moreover, the eventual command signal could have a variable and programmable shape. Such problem coulds, inter alia, be compounded by the embedding of various hardware functionality levels on the same single chip, without the actually realizable scope thereof being known beforehand at the time of finalizing the original design. For example, one might wish to have the microprocessor sample an audio signal at a fixed recurrency, whereas the scope of other tasks could be much more variable.

Accordingly, amongst other things, it is an object of the present invention to provide an inexpensive realisation of such registered counting means that is applicable in, although not limited to an embedded environment, and allowing for uniform program execution as independent from an actual clock frequency and at a variably shapable secondary command signal. This means that the control of delays, periodicity, and shape of command signals would be rendered easier. Now, according to one of its aspects, the invention is characterized in that said counting means comprise

a presettable input section that has said clock input and is arranged for recurrently receiving a variable preset count for counting to said predetermined clock count;

a secondary count section that is fed by said command signal output for counting successive said command signals and for under control of attainment of a predetermined command signal count generating a secondary command signal on a secondary output thereof;

a programmable registered pulse shaper mechanism that is fed by said secondary output for under control of said secondary command signal through serial shifting outputting a shaped version of said secondary command signal.

Advantageously, said sections and said mechanism are mapped on standard memory word lengths of said microprocessor. Specifically, it has been found that the feature of "alternate memory space" that is provided in certain processors, allows for straightforward mapping of one or more of such counting means on available hardware, such at easy accessibility.

The invention also relates to a hierarchical interrupt system for use with the above. Especially in case of various such registered timing means it has been found advantageous to allow for a plurality of interrupts, which are found to be easily manageable through the use of a hierarchization that may include parallel registers, masking and other features that by themselves could be conventional.

Various advantageous aspects of the invention are recited in dependent claims.

Now, these and other aspects of the invention are discussed in detail with respect to the appended exemplary and non-limitative preferred embodiment, as further shown in and by the following figures that respectively represent:

FIG. 1 a block diagram of a counting means as specified;

FIG. 2 a block diagram of a pulse shaper mechanism;

FIG. 3 a block diagram of a microprocessor with embedded additional functionality;

FIG. 4 a hierarchical interrupt system for use with the present invention.

FIG. 1 is a block diagram of a counting means as specified according to the invention. Element 20 is a clock that may be the internal clock of the microprocessor in question. Elements 22, 24, 26 constitute a 64 bit register storage area. Register 22 has 32 bits and is arranged for downcounting to zero, which corresponds to upcounting to full. Upon generating an output signal, such as a borrow, to preset register 28, register 22 is presettable to the actual content of register 28. As long as clock 20 keeps running the presetting of register 22 recurs. As shown, register 28 may be loaded under software control that is not further shown for brevity. Likewise, the content of register 22 may be read as shown for testing purposes. Indirectly, this would mean the testing of register 28. The output signal of register 22 is input to register 24, that contains 24 bits and is also arranged for downcounting to zero under control of the counting pulses received from register 22. The output from register 24 drives register 30 for presetting register 24 at the actual content of register 30. The output from register 24 drives 8-bit register 26 that contains a programmable pulse shaper mechanism which through serial shifting outputs a shaped version of the command signal so received from register 24. The shaped signal on output 32 may drive appropriate further embedded elements of the microprocessor of which the arrangement of FIG. 1 forms a part. Likewise, external elements may be driven. A simplified version of FIG. 2 could do without the presettability through register 30; in that case register 24 can be arranged for upcounting and attaining of a predetermined count outputting a command signal while also resetting to zero, which generally is more complicated. All registers shown in FIG. 1 are modular at 8 bits, which is a standard length. However, other dimensions would do as well. As shown, also registers 30 and 26 can be loaded under software control, whereas registers 24 and 26 can be read for testing purposes.

FIG. 2 is a block diagram of a pulse shaper mechanism according to the invention, that is realizable in register 26 of FIG. 1. Shown are five bit stages or flipflops 40 through 48 and selected interconnections therebetween. All bits are directly loadable from the software in a manner not shown. In particular, control thereto has been omitted. The overall input from register 24 as shown is to stage 40. Stages 40 to 48 are connected as a shift register, that has a shift pulse input 56; this may be fed in various ways by an appropriate frequency. The overall output is from stage 48. The content 0/1 of stage 50 controls the retrocoupling between stages 46 and 40, through a multiplexer functionality 51. If the retrocoupling is directly from stage 40, the contents thereof will continuously be reproduced. If the retrocoupling is from stage 46, a sequence of four bits will continuously be reproduced. Finally, the retrocoupling may be completely deactivated. First, if the retrocoupling is present from stage 46, loading the stages from left to right with "10101" will present a pattern of "10101010101" as long as shift pulses 56 remain active. Likewise, patterns "1000100010001.." and "0000100010001.."0 are feasible. If the retrocoupling is from stage 40, this may cause shaped commands like "11111 . . . ", "0111 . . . ", "000011111 . . . ", or their inverses. If the retrocoupling is absent, the first value p1 loaded into stage 40 is the borrow signal from register 24, the second bit p2 is loaded one clock pulse later, the third bit p3 is the next borrow signal from register 24, the fourth bit p4 is loaded one clock later. Absent register 30, the latter two are continually repeated. The clock pulses on input 56 may be the same as those from clock 20 in FIG. 1, but other sources would be feasible as well.

FIG. 3 is a block diagram of a single-chip microprocessor 70 with embedded additional functionality according to the invention. No further detailing on the register level is presented. Various subsystems are as follows. Clock 20 is the same as the one shown in FIG. 1. In certain situations, various parallel clocks may be present. Block 72 is an arithmetic and logic unit, that may be parameterized. Block 74 is a memory management unit of appropriate functionality level (cache, segmentation, paging, protection, etcetera). Block 76 is on-chip RAM. Sparc has a mapping mechanism onto an alternate memory that is part of a virtual memory and which has been symbolized by block 78, but which is not an additional hardware element of the processor. Available virtual address space is 32 bits wide in the Sparc architecture. Advantageously, the registered counting means is mapped on one of these alternate memory spaces: each such alternate memory address accommodates all register space used in FIG. 1, inclusive of preset registers. The loading and testing is done externally to such alternate memory address. Block 80 represents any further embedded functionality of which the effect is not needed for the present disclosure, but which receives the command signals emanated from the arrangement of FIG. 1. These command signals may also be used externally to the microprocessor in question. Block 82 represents further hardware provisions of the microprocessor. For brevity, the interconnections between the various subsystems in FIG. 3 have not been shown.

FIG. 4 shows a hierarchical interrupt system for use with the present invention. The microprocessor according to FIG. 3 may allow for sixteen interrupts on wires 108 that are coded according to four bit channel 100, after determination of priority thereamong. This particular functionality has not yet been provided in Sparc, but the present inventor has found the need therefor as pressing. Priority may be determined in logic circuitry 102. Mask register 104 allows programmable masking or blocking of certain interrupts. Furthermore, there is input register 106 that can store interrupt flags or surges as they arrive on their associated input 108. As shown the mask register can be loaded along a write channel. Also, both mask register 104 and data register 106 may be read along read channels for testing purposes.

Now if within a certain microprocessor there occur various of the registered counting means according to the foregoing or other local or external interrupt, the arrangement 102/104/106 would become insufficient. Therefore, FIG. 4 has a second hierarchy layer of element 110 that is built according to the same principles as 102-106, inclusive of the loadability and readability features of elements 102/4/6. Block 110 itself feeds a single input of bundle 108. In this way, a multitude of inputs can be handled. The only thing not present in the arrangement is the signalling back to the sources of wires 112, which one is granted interrupt handling priority. Such acknowledge could be generated at the system level.