Data processor capable of treating interrupt at a high speed

Abstract: A data processor comprises a central processing unit; an interrupt request generating means for generating a processing request in asynchronism with the central processing unit; an interrupt controller receiving the processing request from the interrupt request generating means; and a data memory for storing processing data. The interrupt request generating means is capable of selectively generating a first processing request which requests to start a first data processing branching an operation to a predetermined address after saving contents of a program counter and a program status word of the central processing unit to the data memory, and a second processing request which requests to start a second data processing while maintaining contents of the program counter and the program status word. The data memory stores control information for executing the second data processing. The interrupt controller receives the first and second data processing requests from the interrupt request generating means, and operates to output to the central processing unit an interrupt request signal corresponding to a received processing request. The central processing unit receives the interrupt request signal from the interrupt controller, and operates to interrupt execution of an instruction being executed and to selectively start either the first data processing or the second data processing. Thereafter, the central processing unit operates to start the interrupted instruction execution after the started first or second data processing has been completed. Furthermore, the central processing unit operates to continuously execute the second data processing on the basis of the control information stored in the data memory.

Description: Background of the Invention Field of the invention The present invention relates to a data processor, and more specifically to improvement of a single chip microcomputer capable of treating a processing request (namely, interrupt request) sent in an asynchronous manner from a device external to a central processing unit (called "CPU" in the specification) Description of related art Data processors including microcomputers are adapted to process a series of data by sequentially reading and executing a program stored in a memory. In response to a processing request other than an ordinary programed processing, the data processors generally operates to acknowledge an interrupt request, and to interrupt execution of a program which is been executed when the interrupt request is received, and further to read and execute a program corresponding to the acknowledged interrupt request. In conventional data processors, actually, after the interrupt request is sent to the CPU from an external device (namely, an interrupt source), the data processor operates to save contents of a program counter and a program status word, and also to save contents of general purpose registers initialize the general purpose registers. Thereafter, the data processor starts an interrupt subroutine corresponding to the interrupt request. Accordingly, a long time will be consumed after the interrupt request is sent to the CPU until the interrupt program is actually executed. Particularly, the saving of the program counter and the program status word, and the saving and initialization of the general purpose registers are a matter foreign to the data processing required for the interrupt processing. As a result, the interrupt will greatly decrease a data processing capacity of the CPU in the conventional data processor. From Patent Abstracts of Japan, Vol. 12, No. 368 (P-766) (3215), 4.10.1988, JP-A-63 118 949, 23.05.1988, an information processor according to the preamble of claim 1 is known. In this processor, when an I/O request is processed the program counter, the program status word and the universal register group are not updated. Summary of the Invention Accordingly, it is an object of the present invention as it is defined in the appended claims to provide a data processor which has overcome the above mentioned defect of the conventional one. Another object of the present invention is to provide a data processor capable of minimizing the decrease of the processing capacity of the CPU caused by interrupt request processings. The above and other objects of the present invention are achieved in accordance with the present invention by a data processor comprising a central processing unit having an execution unit, a program counter for supplying an address for an instruction to be executed, and a program status word for holding an execution status of a program; an interrupt request generating means for generating a processing request in asynchronism with the central processing unit; an interrupt controller receiving the processing request from the interrupt request generating means; and a data memory for storing processing data. The interrupt request generating means is capable of selectively generating a first processing request which requests to start a first data processing branching an operation to a predetermined address after saving contents of the program counter and the program status word to the data memory, and a second processing request which requests to start a second data processing while maintaining contents of the program counter and the program status word. The data memory stores control information for executing the second data processing. The interrupt controller receives the first and second data processing requests from the interrupt request generating means, and operates to output to the central processing unit an interrupt request signal corresponding to a received processing request. The central processing unit receives the interrupt request signal from the interrupt controller, and operates to interrupt execution of an instruction being executed and to selectively start either the first data processing or the second data processing. Thereafter, the central processing unit operates to start the interrupted instruction execution after the started first or second data processing has been completed. Furthermore, the central processing unit operates to continuously execute the second data processing on the basis of the control information stored in the data memory. In a preferred embodiment, the second data processing is a so-called macro-service, and a series of macro-service processings are sequentially performed on the basis of macro-service control information stored in the data memory. The above and other objects, features and advantages of the present invention will be apparent from the following description of preferred embodiments of the invention with reference to the accompanying drawings. Brief Description of the Drawings Figure 1 is a block diagram of an embodiment of the data processor in accordance with the present invention; Figure 2 illustrates a first example of a memory area allocation within the data memory shown in Figure 1; and Figure 3 illustrates a second example of a memory area allocation within the data memory shown in Figure 1. Description of the Preferred embodiments Referring to Figure 1, there is shown a block diagram of an embodiment of the data processor in accordance with the present invention. The shown data processor includes a CPU 10 having an address bus 12 and a data bus 14 extending therefrom. A program memory 16, a data memory 18 and an interrupt controller 20 are coupled to the address bus 12 and the data bus 14, respectively. The interrupt controller 20 is connected to receive an interrupt request from an interrupt source 22. In most of actual applications, there are a plurality of interrupt sources. However, in Figure 1, for simplification of the drawing, all interrupt sources are represented by the single interrupt source 22. The interrupt controller 20 includes interrupt request flags 24 used for each interrupt request from the interrupt source, and mode designation flags 26 also used for each interrupt request from the interrupt source. When both of the interrupt request flag 24 and the mode designation flag 26 are set, the interrupt controller 20 operates to output a macro-service processing request to the CPU 10. On the other hand, when the interrupt request flag 24 is in a set condition but the mode designation flag 26 is in a cleared condition, the interrupt controller 20 operates to output an interrupt processing request to the CPU 10, similarly to the conventional data processor. The interrupt request flag 24 is cleared in response to a CRQ signal explained hereinafter, when the CPU 10 acknowledges the interrupt request. On the other hand, the mode designation flag 26 is cleared in response to a CME signal explained hereinafter. In addition, the interrupt controller 20 outputs an interrupt vector address or a macro-service storing address to the address bus 12 in response to a VCRD signal explained hereinafter. The interrupt controller 20 also operates to select a request having the highest priority, at each moment, among macro-service requests and interrupt requests from a plurality of interrupt sources, and then to notify the highest priority request to the CPU 10. On the other hand, the CPU 10 includes a temporary register 30, an arithmetic and logic unit (ALU) 32, general purpose registers 34, an instruction register (IR) 36, a program counter (PC) 38, a program status word (PSW) 40, and a timing controller 42, which are coupled to the address bus 12 and the data bus 14 and also coupled to one another, as shown in Figure 1. Since a basic structure of the CPU itself is well known to persons skilled in the art, a detailed explanation will be omitted, and only parts closely relating to the gist of the present invention will be explained. The timing controller 42 is connected through lines 44 and 46 to the interrupt request flag 24 and the mode designation flag 26, respectively, and operates to sample the contents of these flags at a final timing of each instruction processing. Namely, when the timing controller 42 detects that the interrupt request signal 44 is active and the mode designation signal 46 is at a low level, the timing controller 42 controls to the effect that contents of at least the PSW 40 and the PC 38, and if necessary, the general purpose registers 34 are saved to the data memory 18, and thereafter, an operation branching to a predetermined interrupting vector is executed. On the other hand, when the timing controller 42 detects that the interrupt request signal 44 is active and the mode designation signal 46 is at a high level, the timing controller 42 controls to execute the macro-service processing while maintaining the contents of the PSW 40, the PC 38 and the general purpose registers 34. Furthermore, the timing controller 42 outputs the CRQ signal 48 and the CME signal 50 to the interrupt request flag 24 and the mode designation flag 26, respectively. The timing controller also outputs the VCRD signal 52 to the interrupt controller 20. As well known, the program memory 16 stores various programs to be executed by the CPU 10, and the data memory 18 can store a number of items of processing data. In addition, the data memory 18 stores a control data block for realizing the control in accordance with the present invention. Now, an operation of the above mentioned data processor will be explained. In a normal operation, the CPU 10 operates in a such a manner that the content of the PC 38 is outputted to the address bus 12, and an instruction code is read from a designated address location of the program memory 16 through the data bus 14 to the instruction register 36. The timing controller 42 then controls the operation timings of various hardwares including the ALU 32, the general purpose registers 34, etc. Furthermore, the timing controller 42 causes to increment the PC 38 by one instruction code word length in order to generate an address for reading a next instruction code. At a final timing of the instruction processing, the timing controller 42 samples the interrupt request signal 44. If the interrupt request is not detected, the timing controller 42 controls to cause the content of the PC 38 to be outputted to the address bus 12, so that an instruction code is read from the program memory 16. If the interrupt request is detected, the processor operates as follows: If the timing controller 42 detects at a final timing of the instruction processing that the interrupt request signal 44 is active and the mode designation signal 46 is at the low level, the timing controller 42 controls to forcibly set the instruction register 36 with a normal interrupt processing code, so that the processor goes into an interrupt processing. In this interrupt processing, the timing controller 42 causes the contents of the PC 38 and the PSW 40 to be saved to the data memory 18 through the data bus 14. Thereafter, the timing controller 42 activates the VCRD signal 52 for reading an interrupt vector. In response to the activated VCRD signal 53, the interrupt controller 20 outputs an interrupt vector information to the address bus 12, and on the other hand, the timing controller controls to the effect that the vector on the address bus 12 is read out and written to the PC 38. With this, a program is branched to the vector address, and execution of the interrupt processing routine is started. On the other hand, if the timing controller 42 detects at a final timing of the instruction processing that the interrupt request signal 44 is active and the mode designation signal 46 is at the high level, the timing controller 42 controls to forcibly set the instruction register 36 with a macro-service processing code, so that the processor goes into an macro-service processing. This macro-service is a featured function of the data processor in accordance with the present invention. In order to execute the macro-service, the data memory 18 previously stores the control information as shown in Figure 2, which illustrates one example of the data memory allocation. As shown from Figure 2, macro-service control words 200 of the number corresponding to the number of required macro-services are set in the data memory 18. A macro-service control word for each macro-service is composed of two bytes including a control information 200 A and a base address 200B for a macro-service command word explained hereinafter. In addition, as seen from Figure 2, the macro-service control word 200 is directly addressed and designated by the interrupt controller 20 in response to the acknowledged macro-service request. On the other hand, there is provided a macro-service command block 202 including a plurality of macro-service command words 204 (204A, 204B, 204C, ... ). The macro-service command word 204 for each macro-service processing is composed of two bytes including a macro-service mode information 206 (206A, 206B, 206C, ... ) and a memory pointer information 208 (208A, 208B, 208C, ... ). The base address for the macro-service command block 202 is designated by the base address information 200B included in each macro-service control word 200. On the other hand, the memory pointers 208 designate an address of a buffer area within the data memory 18 used for the macro-service. Thus, when the timing controller 42 detects that the interrupt request signal 44 is active and the mode designation signal 46 is at the high level, a macro-service processing is executed in the following procedures: (1-1) The timing controller 42 activates the VCRD signal 52. In response to the active VCRD signal 52, the interrupt controller 20 outputs a macro-service control word storing address of the data memory 18 to the address bus 12. (1-2) The timing controller 42 controls to read a macro-service control word 200 from the data memory 18 on the basis of the macro-service control word storing address outputted onto the address bus 12. The control information 200A within the macro-service control word 200 is transferred to the instruction register 36, and the timing controller 42 starts an initialization for the macro-service, which will be explained below. (2-1) On the basis of the control information set in the instruction register 36, the timing controller 42 controls to the effect that the base address 200B included in the macro-service control word 200 is stored in the temporary register 30, and also is outputted to the address bus 12 so that a macro-service mode information 206A is read from the macro-service command word 204A within the macro-service command block 202 of the data memory. (2-2) Thus, a predetermined macro-service processing is started by setting the macro-service mode information 206A to the instruction register 36. Here, the macro-services can be exemplified by a data transfer between the interrupt source which generates the macro-service request and a buffer area 210 within the data memory 18 designated by the memory pointer information 208A of the macro-service command word 204A, the data transfer being executed while maintaining the contents of the PSW 40, the PC 38 and the general purpose registers 34 as they are. After one macro-service processing has been completed, the following processing is performed for preparation of a next macro-service processing. (3-1) The base address information 200B for the macro-service command block stored in the temporary register 30 is updated (or incremented) by one word, and a new macro-service mode information 206B included in the macro-service command block 202 and corresponding to the updated base address is read out. (3-2) A next macro-service processing is started by setting the newly read-out macro-service mode information 206B to the instruction register 36. As seen from the above, a series of macro-service processings are continuously executed by the reading and execution of a sequence of macro-service mode information 206 from the macro-service command block 202, so that the above steps (3-1) and (3-2) are repeated. As the result of the reading and execution of a sequence of macro-service mode information 206, if an end code is read as the macro-service mode information, it goes to a termination processing of the series of macro-service processings. Namely, the termination processing for the macro-service processings is executed as follows by setting the macro-service end code to the instruction register 36 in the step (3-2) (4-1) In order to notify the termination of the macro-service to the interrupt controller 20, the timing controller 42 activates the CRQ signal 48 so as to clear the corresponding interrupt flag 24. (4-2) The timing controller 42 activates the CME signal 50 in accordance with the type of the macro-service processing, so that the mode designation flag 26 is cleared, while maintaining the interrupt flag 24 in the set condition. In this case, since the interrupt request is maintained even after the required macro-service processing has been completed, the CPU 10 starts the interrupt processing. Referring to Figure 3, there is shown a second example of the date memory allocation, which can realize another embodiment of the data processor in accordance with the the present invention. The second embodiment is realized by using the data processor shown in Figure 1. In addition, in Figure 3, codes and area corresponding to those shown in Figure 2 are given the same Reference Numerals, and explanation thereof will be omitted. As seen from comparison between Figures 2 and 3, the second example shown in Figure 3 is such that a branch command is positioned as a final data of the macro-service command block 202 within the data memory 18. In the other points, the two examples are the same. Therefore, the timing controller 42 of the CPU operates in the same manner as the first embodiment, with respect to the detections of the macro-service request and the interrupt request, and the starting condition for the macro-service processing and the interrupt processing. In addition, the acknowledging operation for the macro-service request and the reading of the macro-service command word from the macro-service command block are executed as follows, similarly to those of the first embodiment. (3-1) The base address information 200B for the macro-service command block stored in the temporary register 30 is updated (or incremented) by one word, and a new macro-service mode information 206B included in the macro-service command block 202 and corresponding to the updated base address is read out. (3-2) A next macro-service processing is started by setting the newly read-out macro-service mode information 206B to the instruction register 36. As seen from the above, a series of macro-service processings are continuously executed by the reading and execution of a sequence of macro-service mode information 206 from the macro-service command block 202. However, if a branch command is read out, a processing for the branch command is executed as follows: (4-1) A branch command information 206C included in the macro-service command block 202 is read out, and then, set to the instruction register 36. (4-2) On the basis of the branch command information set in the instruction register 36, the timing control circuit 42 controls to read the address information 208C for a branch destination or new macro-service command block 302. (4-3) From the new macro-service command block 302, there is read a macro-service command word 304A, and a macro-service mode information 306A included in the read-out macro-service command word 304A is set to the instruction register 36. With this, a series of macro-service processing defined by the new macro-service command block 302 is started. Thus, the macro-service command words 304A, 304B, ... are sequentially read out, and the above steps (3-1) and (3-2) are repeated. As a result, the macro-service processings defined in a plurality of macro-service control blocks are continuously performed. Finally, similarly to the first embodiment, the terminating processing for the macro-service is performed by setting a macro-service end code to the instruction register 36, and then, after the series of macro-service processings are completed, the operation goes into the normal instruction processing. As seen from the above explanation, the data processor in accordance with the present invention is such that a plurality of macro-service control commands for starting a required number of macro-services can be set within the macro-service command block in the data memory. Therefore, a plurality of required programmable macro-services can be executed with a single macro-service request. Furthermore, the data processor in accordance with the present invention can continuously executes a series of macro-services, without saving the execution environment including the PSW and the PC, and also without initializing the execution environment. Therefore, it is possible to decrease the processing capacity of the CPU when an interrupt is generated. The invention has thus been shown and described with reference to the specific embodiments. However, it should be noted that the present invention is in no way limited to the details of the illustrated structures but changes and modifications may be made within the scope of the appended claims.

Claims: A data processor comprising a central processing unit (10) having an execution unit, a program counter (38) for supplying an address of an instruction to be executed and a program status word (40) for holding an execution status of a programm; and a data memory (18) for storing processing data, characterized by an interrupt request generating means (22) for generating a processing request in asynchronism with the central processing unit (10); an interrupt controller (20) receiving the processing request from the interrupt request generating means; the interrupt request generating means being capable of selectively generating a first processing request (44) which requests to start a first data processing branching an operation to a predetermined address after saving contents of the program counter (38) and the program status word (40) to the data memory (18), and a second processing request (46) which requests to start a second data processing while maintaining contents of the program counter (38) and the program status word (40), the data memory (18) storing control information (200A) for executing the second data processing, the interrupt controller (20) receiving the first and second data processing requests (44, 46) from the interrupt request generating means (22) and operating to output to the central processing unit (10) an interrupt request signal corresponding to a received processing request, and the central processing unit (10) receiving the interrupt request signal from the interrupt controller (20) and operating to interrupt execution of an instruction being executed and to selectively start either the first data processing or the second data processing, the central processing unit (10) operating to start the interrupted instruction execution after the started first or second data processing has been completed, the central processing unit (10) operating to continuously execute the second data processing on the basis of the control information stored in the data memory (18). A data processor claimed in claim 1 wherein the interrupt controller (20) responds to a macro-service processing request (46) from the interrupt request generating means (22) so as to directly access to the data memory (18) for reading a control information corresponding to the received macro-service processing request and setting the program counter (38) with the base address (200B) for a requested macro-service, so that the program counter is incremented by a predetermined value at every time the central processing unit (10) executes the macro-service processing, with the result that the central processing unit (10) continuously executes a series of macro-service processing without requiring a macro-service request for each macro-service.

Inventors: KATORI SHIGETATSU, KATORI, SHIGETATSU
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1989
Main classification: G06F9
IPC codes: G06F9