JPH0736150B2 - Barrel shift circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arithmetic circuit of a microcomputer, and more particularly to a barrel shift circuit suitable for shifting and rotating an operand having a plurality of data lengths.

[Background of the Invention]

As shown in FIG. 9, an instruction which is generally executed by a microcomputer in the past includes an arithmetic right shift, an arithmetic left shift, a logical right shift, a logical left shift, a right rotation, a left rotation, and a flag. There are digit movement instructions such as right rotation including and left rotation including flag. The arithmetic unit of the conventional microcomputer that executes this digit shift instruction has the configuration of the block diagram shown in FIG. In the figure, 201 is a register, 202 is an arithmetic and logic unit (ALU), 203 is a shifter for executing a digit shift instruction, and 204, 205 and 206 are registers 20.
This is a system bus for connecting 1 and ALU202. The data in the register 201 is operated by the arithmetic logic operation unit ALU202 via the system buses 204 and 205,
It is stored in the register 201 via 206. Further, the shifter 203 provided in the subsequent stage of the arithmetic logic operation unit ALU202 has conventionally been a small-sized one that shifts right 1 bit and left 1 bit. Therefore, the N-bit digit shift instruction is conventionally executed by repeating the 1-bit shift N times. Therefore, it takes a long time to execute the N-bit digit shift and has a drawback that the operation speed is slow.

Therefore, in order to execute the digit shift instruction at high speed, a digit shift arithmetic unit as shown in FIG. 17 is provided. In the figure, 303 is a circuit for fetching data from the system bus 204, 304 is a barrel shift circuit, and 305 is a circuit for outputting digit-shifted data to the system bus 206. This digit shift circuit has a configuration as shown in FIG. 18 (CARVER MEAD and “IN IN” by LYNN CONWAY).
TRODUCTION TO VLSI SYSTEMS ", page 159). In the figure, 601a to 601d are input lines, 602a to 602d are output lines, and 603a to 603d are control lines. In the figure, input line 601a
The data input from ˜601d are output to the output lines 602a to 602d through MOS (Metal Oxide Semiconductor) transistors selected by any of the control lines 603a to 603d. This conventional circuit shown in FIG. 18 has a drawback that it can perform logical shift at high speed, but cannot perform rotation.

[Object of the Invention]

An object of the present invention is to provide a barrel shift circuit that can individually execute a digit movement instruction such as rotation for data having a predetermined data length.

[Outline of Invention]

The present invention comprises a first control line for determining the digit shift amount of input data and a second control line for determining whether the digit shift of the input data is shift or rotation, and the n-bit input data is simultaneously determined by a predetermined number of bits. In a barrel shift circuit that shifts or rotates, a first shifter that shifts input n-bit data by a predetermined number of bits, a second shifter that shifts input n-bit data by a predetermined number of bits, and the first shifter. Circuit connecting means provided between the shifter and the second shifter for varying the data length of the input data, and the circuit connecting means respectively comprises a pair of diagonal lines and folded lines of the first shifter. And a plurality of switch circuits for connecting between the pair of diagonal lines and the folded line of the second shifter, and a third control line for controlling the operating state of the plurality of switch circuits. Each switch circuit has a pair of diagonal lines and a folding line of the first shifter and a pair of diagonal lines and a folding line of the second shifter, which corresponds to the first shifter of the first shifter according to the signal level of the third control line. The diagonal line is connected to the diagonal line of the second shifter, and the folded line of the first shifter is connected to the folded line of the second shifter, or
The shifter is controlled so as to connect the pair of diagonal lines and the turn-back line, and to connect the pair of diagonal lines and the turn-back line of the second shifter.

Example of Invention

Hereinafter, embodiments of the barrel shift circuit according to the present invention will be described with reference to the drawings. The operation of the barrel shift circuit according to the present invention will be described with reference to FIG.

In the figure, 401a to 401d are input lines, 402a to 402d are output lines,
42a to 42d, 43a to 43d, 44a to 44d, 45a to 45d, 46a to 46d are switches for connecting the input line and the output line (subscript a of each numeral a
Bits marked with are lower, bits marked with d are higher). Further, 403 to 407 are control lines for controlling the opening and closing of the switches. 415 to 418 are diagonal lines connected to the input line. Further, 411 to 414 are diagonal lines that are not connected to the input line. The state shown in FIG. 2 shows that the switches 45a to 45d connected to the control line 406 are closed. In this state, it is assumed that 4-bit data of a ₀ , a ₁ , a ₂ , a ₃ is input to the input line. For example, the data input to the input line 401b is output to the output line 402c via the diagonal line 417 and the switch 45C.
Is output from. Similarly, data input from the input line 401a is output to the output line 402b, and data input from the input line 401c is output from the output line 402d. Also, output line 40
A diagonal line 411 that is not connected to any of the input lines 401a to 401d is connected to 2a. If the diagonal line 411 is set to the voltage corresponding to the logic "0", the value output from the output line 402a will be "0". That is, the output lines 402a, 402
Data of “0”, “a ₀ ”, “a ₁ ”, and “a ₂ ” are output to b, 402c, and 402d, and 1-bit logical left shift is performed. Similarly, by closing the other switches, the left 2
Logical shift of bit, left 1 bit, left 0 bit, right 1 bit, right 0 bit can be calculated at one time. Further, FIG. 2 shows an example in which the data length is 4 bits and the shift amount is 2 bits on the left and right. However, increasing the data length and the shift amount can be easily realized by increasing the same switch cell.

FIG. 3 shows the switches 42a to 42d, 43a to 43d, 44a shown in FIG.
~ 44d, 45a ~ 45d, 46a ~ 46d is a barrel shift circuit constituted by N-type MOS transistors. In the figure, 403, 404, 405, 406 and 407 are control lines, 401a to 401d are input lines, 4
02a to 402d are output lines. In addition, 204a to 204d of FIG.
206a to 206d are system buses in FIG. The circuit shown in FIG. 3 is a circuit for logically shifting left and right.

FIG. 4 shows a barrel shift circuit that rotates the input data left and right. The circuit configuration is almost the same as that of the barrel shift circuit shown in FIG. 3, but is different from the barrel shift circuit shown in FIG. 4 in that folding lines 702 to 705 are added.
This is different from the barrel shift circuit shown in the figure. That is,
In the barrel shift circuit shown in FIG. 3, the diagonal line 504, which is not connected to the input line, is connected to the input line 401c by the folded line 705 via the diagonal line 507. Similarly, diagonal lines 503, 501, 502 are connected to input lines 401d, 401b, 401a by folding lines 704, 702, 703, respectively. Referring now to FIG. 4, for example, in the input line, "a ₀ ",
By inputting “a ₁ ”, “a ₂ ”, and “a ₃ ”, and setting only 406 of the control lines to the high level, “a ₃ ”, “a ₀ ” is output to the output lines 402a, 402b, 402c, 402d. , “A ₁ ”, “a ₂ ” are output. In this way, 1-bit left rotation is calculated. Similarly, according to the barrel shift circuit shown in FIG. 4, it is possible to perform a rotation operation up to two bits on the left and right. However, no logical shift is possible.

FIG. 5 shows a barrel shift circuit capable of operating both logical shift and rotate instructions. The circuit configuration is almost the same as that of the barrel shift circuit shown in FIG. 4, but the barrel shift circuit shown in FIG. 5 is provided with MOS transistors 803 to 806 between the diagonal lines of the folded lines.
Control line for controlling on / off of OS transistors 803-806
801 is added, which is different from the barrel shift circuit shown in FIG. In the barrel shift circuit shown in FIG. 5, if the control line 801 is set to low level and the MOS transistors 803, 804, 805, 806 are turned off, a logical left / right shift instruction can be calculated. If the control line 801 is set to high level and the MOS transistors 803, 804, 805, 806 are turned on, the rotation command can be calculated.

The barrel shift circuit shown in FIG. 5 has a function of rotating 4-bit data. The barrel shift circuit shown in FIG. 1 is a barrel shift circuit having a function of rotating 4-bit data and 8-bit data. The whole is composed of a 4-bit barrel shift circuit 109 and a 4-bit barrel shift circuit 110. The circuit configuration of the barrel shift circuit 109 is exactly the same as that of the barrel shift circuit shown in FIG. Further, the circuit configuration of the barrel shift circuit 110 is almost the same as that of the barrel shift circuit shown in FIG. The barrel shift circuit shown in FIG. 1 is a circuit for connecting upper 4 bits and lower 4 bits 105 to 1
08 is added. The circuit configuration of the connection circuits 105 to 108 is shown in FIG. In FIG. 6, 901 and 902
Are a diagonal line and a folded line of the barrel shift circuit 109 which are respectively connected to the upper part. In addition, reference numerals 903 and 904 in the figure respectively denote an oblique line and a folded line of the barrel shift circuit 110 connected to the lower part. Further, 905 and 906 in FIG. 6 are control lines for controlling the MOS transistors 907 to 910 and correspond to the control lines 102 and 103 in FIG.

FIG. 7 shows the connection state of each line when the control line 905 in the barrel shift circuit shown in FIG. 6 is set to low level and the control line 906 is set to high level. In the state of FIG. 7, the diagonal line 901 and the folded line 902 in the upper part of FIG. 6 are connected, and the diagonal line 903 and the folded line 904 in the lower part are connected to each other. Further, since the MOS transistors 908 and 909 are turned off, the upper circuit and the lower circuit are separated.

Further, FIG. 8 shows the connection state of each line when the control line 905 is set to the high level and the control line 906 is set to the low level. In this case, the upper diagonal line 901 and the lower diagonal line 903, and the upper folding line 902 and the lower folding line 904 are connected, respectively. Further, the MOS transistors 907 and 910 are turned off, and the upper barrel shift circuit 109 and the lower barrel shift circuit 110 are connected.

The operation of the barrel shift circuit shown in FIG. 1 will be described from the above description. If the control line 101 in FIG. 1 is set to high level, the control line 102 is set to high level, and the control line 103 is set to low level,
A rotation instruction of 8-bit data can be calculated. Meanwhile, the control line
101 is high level, control line 102 is low level, control line 103
Is set to a high level, the upper 4-bit data and the lower 4-bit data can be independently rotated. Similarly, if the control line 101 is set to low level, 8-bit data, 4
A logical shift instruction of bit data can be calculated.

As described above, according to the present embodiment, the first control line for determining the digit shift amount of the input data and the second control line for determining whether the digit shift of the input data is shift or rotation are provided, and n bits are included. In the barrel shift circuit that simultaneously shifts or rotates the input data of a predetermined number of bits, by providing a circuit connecting means for varying the data length of the input data between the first shifter and the second shifter, a predetermined data length is obtained. It is possible to individually execute a digit movement command such as rotation for the above data at high speed.

FIG. 10 shows the configuration of an embodiment of the barrel shift circuit according to the present invention.

In the figure, 1332 to 1336 are control lines for controlling the shift amount. Further, C0 to C6 are control lines for controlling the function of the barrel shifter. Further, the portion of 1300 is shown in FIG. Also,
The portion of 1308 and 1316 shown in FIG. 10 is shown in FIG.
The portion 1331 shown in FIG. 10 is shown in FIG. The remaining portions 1301 to 1307, 1309 to 1315, 1317 to 1330 are shown in FIG.

The operation of the circuits shown in FIGS. 12 and 14 is clear from the description of FIGS. 3, 4, and 5. The circuit in FIG. 11 is a circuit for controlling the connection between the barrel shift circuit on the upper side and the barrel shift circuit on the lower side. Since 8-bit and 16-bit data can be rotated only in the lower order, two of the four connection MOS transistors shown in FIG. 6 can be omitted.

In FIG. 13, 1605 is an input line from the flag, and 1606 is an output line to the flag. Also, MOS transistors 1612 to 1623
Is for controlling whether or not the rotation includes a flag.

FIG. 9 illustrates the operation of these embodiments. 8
Performs arithmetic left / right shift, logical left / right shift, left / right rotation, and left / right rotation including flags on bit, 16-bit, and 32-bit length data, respectively. However, 8-bit operation is performed only on the upper 8 bits, and 16-bit operation is performed only on the upper 16 bits. The shift amount is 2 on the left
Bit, right 2 bits.

FIG. 15 summarizes the logic of the control lines when executing each operation. However, before the operation of 8-bit arithmetic right shift, it is necessary to write "0" or "1" in the upper bits according to the sign of the complemented 8-bit data. The same applies to 16-bit arithmetic right shift. Also, for 32-bit arithmetic right shift, control line C6
The diagonal line separated from the input line must be fixed to "1" or "0" depending on whether the 32-bit data is positive or negative. Although these are not described in detail, they are operations that can be easily realized.

Therefore, according to this embodiment, there are advantages of high speed and multi-function.

〔The invention's effect〕

As described above, according to the present invention, various digit shift operations such as logical shift, rotation, rotation including a flag, etc. can be simultaneously performed for data of a predetermined data length by a predetermined number of bits at the same time.
This has the effect of increasing speed and increasing functionality.

[Brief description of drawings]

FIG. 1 is a circuit diagram for explaining the barrel shift circuit of the present invention, FIG. 2 is a diagram for explaining the operation of the barrel shift circuit of the present invention, and FIG. 3 is for explaining the operation of FIG. FIG. 4, FIG. 4 is a diagram for explaining the operation of FIG. 2, FIG. 5 is a diagram showing a barrel shift circuit of the present invention, FIG. 6 is a diagram showing a part of the circuit shown in FIG. 7 and 8 are diagrams for explaining the operation of the circuit shown in FIG. 6, FIG. 9 is a diagram for explaining the operation of the embodiment of the present invention, FIG. 10 is a block diagram showing the embodiment of the present invention, and FIG. FIG. 12, FIG. 13, FIG. 13 and FIG. 14 are partially enlarged circuit diagrams of the circuit shown in FIG. 10, FIG. 15 is a diagram showing the logic of the control line of the embodiment shown in FIG. 10, and FIG. FIG. 17 is a block diagram showing a digit shift instruction execution system, FIG. 17 is a block diagram showing a digit shift instruction execution system having a barrel shift circuit, and FIG. 18 is a block diagram showing a conventional barrel shift method. FIG. 109 ... Lower 4 bit barrel shift circuit, 110 ... Higher 4 bit barrel shift circuit, 105-108 ... Connection circuit, 101-103 ... Control line.

Claims (1)

[Claims] 1. A first control line for determining a digit shift amount of input data, and a second control line for determining whether a digit shift of input data is a shift or a rotation. In a barrel shift circuit that simultaneously shifts or rotates, a first shifter that shifts input n-bit data by a predetermined number of bits, a second shifter that shifts input n-bit data by a predetermined number of bits, and A circuit connecting means provided between the first shifter and the second shifter for varying the data length of the input data, wherein the circuit connecting means includes a pair of diagonal lines and a folded line of the first shifter. A plurality of switch circuits for connecting between a line and a pair of diagonal lines and a folded line of the second shifter, and a third control line for controlling an operating state of the plurality of switch circuits, Each of the plurality of switch circuits includes a first of the pair of diagonal lines and the folding line of the first shifter and the pair of the diagonal line and the folding line of the second shifter according to the signal level of the third control line. The diagonal line of the shifter and the diagonal line of the second shifter are connected to each other, and the folding line of the first shifter and the folding line of the second shifter are coupled to each other, or the pair of diagonal lines of the first shifter is connected to each other. A barrel shift circuit, which is controlled so as to connect a folding line and a pair of diagonal lines of the second shifter and the folding line.