Control device having a function of modifying a microinstruction

Abstract: A control device includes a memory storing a plurality of micro instructions. A modifying information generator generates modifying information. A modifying unit receives one of the micro instructions and the modifying information from the memory and the modifying information generator respectively. The modifying unit modifies at least part of the one of the micro instructions with the modifying information.

Description: This invention relates to a device in a computer which controls an arithmetic unit in a method using a microprogram. Japanese published unexamined patent application 62-143138 discloses a device in a computer which controls an arithmetic unit in a method using a microprogram. The control device of the application 62-143138 has a function of modifying a microinstruction. In the application 62-143138, the modifying function is limited only to a disabling function. Document D1, EP-A-0,184,158, discloses a controller for a microprocessor which includes a memory (ROM 201) for storing a plurality of micro-instructions. A field programmable logic array (FPLA 204) receives an operand field of a macro-instruction and generates the appropriate control bits of the micro-instruction. The output of the ROM 201 and the FPLA 204 are received as inputs to the MUX 202. The MUX 202 is controlled to selectively modify the micro-instruction by replacing the information from the ROM 201 with the control bits from the FPLA 204 to thereby form a modified micro-instruction. D1 selects between an unmodified micro-instruction operand and a modified micro-instruction operand in response to the output of the decoder 206. The decoder 206 is responsive to a micro-instruction, however, that micro-instruction is the modified instruction from a previous operation as held in register 205, not the same micro-instruction now retrieved from the control ROM 201. D1 uses the first retrieved micro-instruction to establish the initial state of the select signal output by the decoder 206. It is an aim of this invention to provide a control device having a function of modifying a microinstruction. According to the present invention, there is provided a control device which executes steps of operation clock-period by clock-period, comprising: a decoder for decoding a macro instruction into address information and control information during a first clock-period; a memory, connected to the decoder via an address generator to receive the address information therefrom, for storing a plurality of micro instructions and for selecting and outputting one of the micro instructions in response to the address information during a second clock-period after the first clock period; a controller, connected to the decoder to receive the control information therefrom, for generating a control signal in response to the control information during the second clock-period; a modifying information generator, receiving the macro instruction and being connected to the controller to receive the control signal therefrom, for generating during the second clock period first modifying information from the macro instruction in response to the control signal ; and a modifying unit, connected to the memory and the modifying information generator to receive said one of the micro instructions and the modifying information therefrom, for modifying at least part of said one of the micro instructions with the modifying information during the second clock period. The present invention will be further described hereinafter with reference to the following description of an exemplary embodiment and the accompanying drawings, in which: Fig. 1 is a block diagram of a control device according to an embodiment of this invention. Fig. 2(a) is a block diagram of a portion of the modifying unit of Fig. 1. Fig. 2(b) is a block diagram of another portion of the modifying unit of Fig. 1. Fig. 3 is a timing diagram showing an example of basic operation of the control device of Fig. 1 which occurs during an instruction decoding process. Fig.4 is a diagram showing two different formats of a macro instruction for the data transfer between registers. Fig. 5 is a block diagram of the controllers of Fig. 1. With reference to Fig. 1. a control device includes a memory 1 which stores a plurality of micro instructions. A modifying information generator 2 composed of a PLA (a programmable logic array) generates information for modifying a micro instruction. A modifying unit 3 receives a micro instruction 14 and modifying information 15 from the memory 1 and the modifying information generator 2 respectively, and executes a process of modifying the micro instruction 14 by the modifying information 15. Data to be input into the modifying information generator 2 are selected from a plurality of pieces of data by a selector 4, and the selected data are stored into an input register 5. An address generator 6 outputs an address signal (simply referred to as an address hereinafter) to the memory 1. A decoder 7 decodes a macro instruction 16. The modifying information generator 2 is controlled by a controller 8. The modifying unit 3 is controlled by a controller 9. A bit modifying unit 10 modifies data in a predetermined bit of the input register 5. A stack unit 11 functions to save the data stored in the input register 5 and to return the saved data to the input register 5. An arithmetic unit or an execution unit 12 receives a modified micro instruction from the modifying unit 3 and executes the instruction. The arithmetic unit 12 includes an ALU main part and a general register. An interruption reception unit 13 stores information of interruption factors. Fig. 2(a) shows a portion of the modifying unit 3 which functions to modify predetermined information within a micro instruction, the predetermined information being outputted as control information. Specifically, this portion of the modifying unit 3 functions to modify an operation field, two source operand fields, and a destination operand field of a micro instruction 14 by modifying information 15 of an operation field, two source operand fields, and a destination operand field in accordance with control information 17 outputted from the controller 9. The operation field designates operation to be executed by the arithmetic unit 12. The modifications of the four fields are mutually independent. The control information 17 has four bits corresponding to the respective four fields. In addition, the modifying unit 3 has four AND gates 3A and four OR gates 3B corresponding to the respective four fields. When a bit of the control information 17 is "1", the corresponding AND gate is open so that modifying information 15 of the corresponding field is transmitted to the corresponding OR gate and an "OR" operation between the modifying information 15 and the micro instruction 14 of the field is executed. When a bit of the control information 17 is "0", the corresponding AND gate is closed so that the transmission of the corresponding field of the modifying information 15 to the corresponding OR gate is inhibited and the modification of the field of the micro instruction 14 is also inhibited. Fig. 2(b) shows another portion of the modifying unit 3 which functions to modify predetermined information within a micro instruction, the predetermined information being outputted to the arithmetic unit 12 as data. Specifically, this portion of the modifying unit 3 includes a selector 26 operative to select fields of a micro information 14 and modifying information 15 which are used as data. This selection is controlled by control information 17 outputted from the controller 9. Generally, a micro instruction is of a plurality of types. A type field of a micro instruction denotes a type of the micro instruction. Fields of a micro instruction which are used as data are dependent on the type of the micro instruction. In view of this fact, data selected by the selector 26 are expanded in size by an expander 27 in accordance with the type field of a micro instruction 14, and the resultant data 23 are outputted to the arithmetic unit 12. As shown in Fig. 4, a macro instruction for the data transfer between two registers (reg0 and reg1) has two different formats denoted by FORMAT 1 and FORMAT 2 respectively. The information inputted into the modifying information generator 2 is represented by "input=[cont, data]" where "cont" denotes the output signal from the controller 8 and "data" denotes the output signal from the input register 5. The PLA of the modifying information generator 2 is programmed to execute the following operation. In the case of FORMAT 1: if cont = reg_of_format1 then modifying information (source operand) = [b'00', data[2:5]]; modifying information (destination operand) = [data[6:7], data[12:15]]; In the case of FORMAT 2: if cont = reg_of_format2 then modifying information (source operand) = [data[6:7], data[12:15]]; modifying information (destination operand) = [b'00' , data[2:5]]; The overall modifying operation will be explained hereinafter. In the case of FORMAT 1: Before Modification micro instruction (operation) = "mov" micro instruction (source operand) = [b'10', b'0000']; where "b'10'" corresponds to size=word; micro instruction (destination operand) = [b'00', b'0000']; control information 17 (operation) = 0 control information 17 (source operand) = 1 control information 17 (source operand) = 0 control information 17 (destination operand) =1 After Modification micro instruction (operation) = "mov" micro instruction (source operand) = [b'10', data[2:5]]; micro instruction (destination operand) = [data[6:7], data[12:15]]; In the case of FORMAT 2: Before Modification micro instruction (operation) = "mov" micro instruction (source operand) = [b'00', b'0000']; micro instruction (destination operand) = [b'10', b'0000']; where "b'10'" corresponds to size=word; control information 17 (operation) = 0 control information 17 (source operand) = 1 control information 17 (source operand) = 0 control information 17 (destination operand) =1 After Modification micro instruction (operation) = "mov" micro instruction (source operand) = [data[6:7], data[12:15]]; micro instruction (destination operand) = [b'10', data[2:5]]; As shown in Fig. 5, the controller 8 includes a selector 28 and a decoder 30. The selector 28 selects one of the control information 19 and the control information 22 outputted from the decoder 7 and the memory 1 respectively. This selection will be described in more detail later. The decoder 30 generates a control signal in accordance with the control information selected by the selector 28. The control signal is outputted from the decoder 30 to the modifying information generator 2. The modifying information generator 2 is controlled by the control signal as described later. Similarly, the controller 9 includes a selector 29 and a decoder 31. The selector 29 selects one of the control information 19 and the control information 22 outputted from the decoder 7 and the memory 1 respectively. This selection will be described in more detail later. The decoder 31 generates a control signal 17 in accordance with the control information selected by the selector 29. The control signal 17 is outputted from the decoder 31 to the modifying unit 3. The modifying unit 3 is controlled by the control signal 17 as described later. Fig. 3 shows an example of basic operation of the control device of Fig. 1 which occurs during an instruction decoding process. In this example, instructions "a" and "b" are handled. The instruction "a" is an instruction of operation between registers which can be executed in one clock period. The instruction "b" is an instruction of operation between a memory and a register which can be executed in two clock periods. The processing of the instruction "a" will be explained hereinafter. A macro instruction for the instruction "a" is fetched at a clock period t1. During a clock period t2 immediately following the clock period t1, the macro instruction is decoded by the decoder 7 so that an entry address 18 and control information 19 are generated by the decoder 7 on the basis of the macro instruction. The entry address 18 is fed to the address generator 6. The control information 19 is fed to the controllers 8 and 9. During a clock period t3 subsequent to the clock period t2, the address generator 6 outputs an address denoted by the entry address 18, and the memory 1 outputs a micro instruction 14 in response to the address fed from the address generator 6. In this case, while the operation field of the micro instruction 14 has information representing an operation to be executed by the arithmetic unit 12, the two source operand fields and the destination operand field are set to "00 ··· 0". The selector 4 selects a macro instruction 16, and sets the macro instruction for the instruction "a" in the input register 5. The controller 8 controls the modifying information generator 2 in accordance with the control information 19, cutting out a register number field from the macro instruction for the instruction "a" and outputting the register number field from the modifying instruction generator 2 as modifying instruction 15. The register number field is necessary in a micro instruction. Specifically, a register number at a source side of the macro instruction is cut out, and the register number is set in a modification field of one of source operands of the modifying information 15. In addition, a register number at a destination side of the macro instruction is cut out, and the register number is set in an operand field and the other source operand field of the modifying information 15. The controller 9 controls the modifying unit 3 in accordance with the control information 19. Specifically, the controller 9 orders the modifying unit 3 to execute an "OR" operation between the micro instruction 14 and the modifying instruction 15 with respect to the two source operand fields and the destination operand field. In addition, the controller 9 orders the modifying unit 3 to inhibit the modification of the micro instruction 14 by the modifying instruction 15 with respect to the operation field. Thus, the desired register numbers are set in the operand fields of the resultant modified micro instruction. During a clock period t4 subsequent to the clock period t3, the arithmetic unit 12 executes a command in accordance with the modified micro instruction fed from the modifying unit 3. The processing of the instruction "b" will be explained hereinafter. The processing of the instruction "b" is similar to the processing of the instruction "a" except for the following points. In general, the instruction "b" is of various types. The instrutction "b" explained here is of a type which makes it necessary to output two micro instructions to the arithmetic unit 12, one micro instruction being used for fetching a memory operand and the other micro instruction being used for operation between the fetched operand and a register. In some cases, the reason for needing two micro instructions is that operand fetch from a memory is necessary in respect of the instruction "b". A macro instruction for the instruction "b" is fetched at the clock period t2. During the clock period t3, the macro instruction is decoded by the decoder 7 so that an entry address 18 and control information 19 are generated by the decoder 7 on the basis of the macro instruction. The entry address 18 is fed to the address generator 6. The control information 19 is fed to the controllers 8 and 9. During the clock period t4, the address generator 6 outputs an address denoted by the entry address 18, and the memory 1 outputs a micro instruction 14 in response to the address fed from the address generator 6. In this case, the operation field of the micro instruction 14 has information representing an operation for the fetch of a memory operand which is to be executed by the arithmetic unit 12, and the destination operand field has a register number of a temporary register. Since it is necessary to output a subsequent micro instruction during a next clock period, the memory 1 feeds the address generator 6 with control information 21 for generating an address of the subsequent micro instruction. In addition, the memory 1 feeds the controllers 8 and 9 with control information for generating modifying information related to the subsequent micro instruction. The selector 4 selects a macro instruction 16, and sets the macro instruction for the instruction "b" in the input register 5. The controller 9 controls the modifying unit 3 in accordance with the control information 19. Specifically, the controller 9 orders the modifying unit 3 to inhibit the modification of the micro instruction 14 by the modifying instruction 15 with respect to the two source operand fields, the destination operand field, and the operation field. Thus, the modifying unit 3 outputs a modified micro instruction identical with the input micro instruction 14. In parallel with the execution of these processes, address calculation of a memory operand is executed. During a clock period t5 subsequent to the clock period t4, the arithmetic unit 12 executes memory fetch in accordance with the modified micro instruction fed from the modifying unit 3. The address for the subsequent micro instruction is outputted from the address generator 6 in response to the control information 21 which is outputted at the preceding clock period t4, and the memory 1 outputs a subsequent micro instruction 14 in response to the address fed from the address generator 6. In this case, while the operation field of the micro instruction 14 has information representing an operation to be executed by the arithmetic unit 12 and one of the source operand fields has a register number of a temporary register, the other source operand field and the destination operand field are set to " 00 ··· 0". The input register 5 continues to store the macro instruction for the instruction "b". The controller 8 controls the modifying information generator 2 in accordance with the control information 22 which is outputted from the memory 1 at the preceding clock period t4, cutting out a register number field from the macro instruction for the instruction "b" and outputting the register number field from the modifying instruction generator 2 as modifying instruction 15. The register number field is necessary in a micro instruction. Specifically, a register number at a destination side of the macro instruction is cut out, and the register number is set in one of the source operand fields and the destination operand field of the modifying information 15. The controller 9 controls the modifying unit 3 in accordance with the control information 22 which is outputted from the memory 1 at the preceding clock period t4. Specifically, the controller 9 orders the modifying unit 3 to execute an "OR" operation between the micro instruction 14 and the modifying instruction 15 with respect to one of the two source operand fields and the destination operand field. In addition, the controller 9 orders the modifying unit 3 to inhibit the modification of the micro instruction 14 by the modifying instruction 15 with respect to the operation field and the other source operand field for which the memory 1 outputs the register number of the temporary register. Thus, the desired register number is set in the operand field of the resultant modified micro instruction. During a clock period t6 subsequent to the clock period t5, the arithmetic unit 12 executes a command in accordance with the modified micro instruction fed from the modifying unit 3. In the case of a macro instruction having a plurality of separate instruction codes, the instruction codes are sequentially inputted into the input register 5 while the processing of the macro instruction is advanced. The stack unit 11 saves the instruction codes stored in the input register 5. When a previous instruction code is required, it is fed from the stack unit 11 and is thus recovered. In the case where the saving and recovering process by the stack unit 11 is performed together with a subroutine of a micro instruction, a flexibility of a micro program is enhanced. In the case where instructions for executing the saving and recovering processes on a plurality of registers have bit sequences denoting the registers, the target register number is updated as the processing is advanced. In such a case, one register number in a bit sequence set in the input register 5 is outputted by the modifying information generator 2 as modifying information 15, and the bit modifying unit 10 modifies the bit of the bit sequence which corresponds to the outputted register number. This process enables an increased speed of processing of a micro program and a simplification of the micro program. The selector 4 is connected to a data bus 24 of the arithmetic unit 12. This design is intended to effectively process an instruction of a high function such as a bit field in which an operation is not designated in a macro instruction but it is designated in a general register within the arithmetic unit 12. The contents of the designated operation are transferred from the arithmetic unit 12 to the input register 5 via the selector 4. The contents of the designated operation are outputted from the input register 5 to the modifying information generator 2. The modifying information generator 2 sets the target operation in the operation field of modifying information 15. The modifying unit 3 executes an "OR" operation between a micro instruction and the modifying information 15 with respect to the operation field. In the case where the sequence of processing an instruction depends on the results of an operation or data in a memory, the target data are transferred from the arithmetic unit 12 to the input register 5 via the selector 4, and the target data are outputted to the modifying information generator 2. The modifying information generator 2 generates branch information 25 on the basis of the target data. The branch information 25 represents judgment conditions for varying a processing sequence and an offset for a multi-direction branch. The branch information 25 is outputted to the address generator 6. This design enables an increased speed of processing of a micro program and an enhanced flexibility of the micro program. During such a branch process, data previously set in the input register 5 are sometimes required. Accordingly, when the target data are set in the input register 5, the previous data in the input register 5 are saved into the stack unit 11. The modifying information generator 2 can be easily realized by using a PLA having a regular structure. The modifying unit 3 has a simple and regular structure. Accordingly, when the modifying unit 3 is composed of an LSI, it occupies only a very small area. As understood from the previous description, one or more fields of a micro instruction outputted from the memory 1 can be disabled by the modifying unit 3. In addition, one or more fields of a micro instruction outputted from the memory 1 can be modified by the modifying unit 3 with modifying information outputted from the modifying information generator 2. As the processing of a micro instruction is advanced, the contents of the modification can be varied in accordance with information stored in the input register 5. Therefore, the flexibility of the modification of a micro instruction is enhanced, and a micro instruction is reduced by making micro instructions common and decreasing the number of steps. The selector 4 is connected to the interruption reception unit 13 which stores information of interruption factors. This design is intended to effectively handle multi-reception of interruption factors, a variation in a process sequence which corresponds to interruption factors, and a variation in an address of an interruption vector to be read during the processing of receiving an interruption. A received interruption factor is transferred from the interruption reception unit 13 to the input register 5 via the selector 4. In the case of multi-reception of interruption factors, the modifying information generator 2 sets judgment conditions for varying a process sequence and an offset for a multi-direction branch with respect to the address generator 6. This design enables a simplified hardware for an interruption process and an enhanced flexibility of an interruption process sequence. The selector 4 enables instruction codes and other information of various types to be used for modifying a micro instruction. The modification of micro instructions allows high-speed processing. This embodiment may be modified as follows. While the modifying unit 3 is controlled by the controller 9 in accordance with the control information 22 outputted from the memory 1 in the embodiment, the control information 22 may be outputted from the modifying information generator 2 or other devices. The modifying information generator 2 may be also used as an arithmetic unit. In addition, the controllers 8 and 9 may be provided with stack devices.

Claims: A control device which executes steps of operation clock-period by clock-period, comprising: a decoder (7) for decoding a macro instruction (16) into address information (18) and control information (19) during a first clock-period; a memory (1), connected to the decoder (7) via an address generator (6) to receive the address information (18) therefrom, for storing a plurality of micro instructions and for selecting and outputting one (14) of the micro instructions in response to the address information during a second clock-period after the first clock period; a controller (8), connected to the decoder to receive the control information (19) therefrom, for generating a control signal in response to the control information during the second clock-period; a modifying information generator (2), receiving the macro instruction and being connected to the controller (8) to receive the control signal therefrom, for generating during the second clock period first modifying information (15) from the macro instruction (16) in response to the control signal; and a modifying unit (3), connected to the memory and the modifying information generator to receive said one of the micro instructions and the modifying information therefrom, for modifying at least part of said one of the micro instructions with the modifying information during the second clock period. A control device according to claim 1 wherein said memory (1) is operative for selecting and outputting a second one of the micro instructions in response to at least part of a first one of the micro instructions during a third clock period following the second clock period; said controller (8) being connected to the memory (1) to receive at least part of said first one of the micro instructions therefrom and being operative for generating a second control signal in response to at least part of said first one of the micro instructions during the third clock period; said modifying information generator (2) receiving the second control signal from the controller (8) and being operative for generating second modifying information in response to the second modifying information in response to the second control signal during the third clock period; said modifying unit (3) receiving said second one of the micro instructions from the memory and the second modifying information from the modifying information generator and being operative for modifying at least part of said second one of the micro instructions with the second modifying information during the third clock period. A control device according to claims 1 or 2, further comprising an input register (5) for storing input data input to the modifying information generator, and wherein the modifying information generator generates the modifying information on the basis of the input data stored in the input register. A control device according to claim 3, further comprising a bit modifying unit (10) connected to the input register for modifying a portion of the selected input data which is contained in a predetermined bit of the input register. A control device according to claims 3 or 4, further comprising a stack unit (11) connected to the input register, the stack unit being adapted to store data output from the input register and to return the output data back to the input register. A control device according to any one of the preceding claims, further comprising an address generator (6) for supplying an address to the memory (1), and wherein the memory is adapted to output a microinstruction to the modifying unit (3) in accordance with the address, the modifying information generator being adapted to output branch information (21) to the address generator, the address generator determining the address on the basis of the branch information. A control device according to any one of the preceding claims, wherein the modifying information generator comprises a programmable logic array. A control device according to any one of the preceding claims, further comprising: a selector (4) for selecting one of the pieces of input data input to it. A control device according to claim 8, further comprising an arithmetic unit (12) connected to the selector (4) for supplying one of the pieces of input data to the selector. A control device according to claim 8 or 9, further comprising an interrupt reception unit (13) for storing interrupt factors and being connected to the selector for supplying one of the pieces of input data to the selector.

Inventors: KIMURA KOZO, KIYOHARA TOKUZO, WATANABE TAKAHIRO, KIMURA, KOZO, KIYOHARA, TOKUZO, WATANABE, TAKAHIRO
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1990
Main classification: G06F9
IPC codes: G06F9