JPH02267624A - Microcomputer - Google Patents

Abstract

PURPOSE:To attain the operation of bits just by writing the necessary data into a pair of registers by giving a write inhibiting or granting function to one of both registers capable of the simultaneous accesses for the bit corresponding to the other register. CONSTITUTION:When a certain bit of an A register 1 is 1, for example, the write is inhibited to the corresponding bit of a B register 2. Then this write is granted when the bit of the register 1 is 0. Here it is supposed that both registers 1 and 2 have the initial value 0H. Under such conditions, 5FH is written at one time to both registers 1 and 2. Thus the register 2 is inhibited to perform the write to the bit whose corresponding bit of register 1 is 1 owing to 5H of register 1; the bit is kept at initial value 0. While the register 2 is granted to perform the write to the bit whose corresponding bit is 0. Therefore the initial value is rewritten to 1 from 0 and the value of the register 2 is finally set at AH. As a result, the operation of bits is attained just with the write of a single time to both registers 1 and 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to microcomputers (hereinafter referred to as microcomputers), and particularly relates to improvements in bit operations of registers thereof.

[Conventional technology]

An example of bit manipulation in a conventional microcomputer will be explained using the flowchart shown in FIG. To perform bit operations such as setting or clearing a specific bit in a register, first read the value of the register (step S1), perform some processing on that value (step S2), and read out the processed value again in the register. (step 33).

[Problem to be solved by the invention]

Since bit operations in conventional microcomputers are performed as described above, the overhead for bit operations cannot be ignored, and there have been problems such as the inability to keep up with high real-time applications.

The present invention has been made to solve the problems of the conventional devices as described above, and an object of the present invention is to provide a microcomputer that can eliminate the overhead associated with register bit operations.

[Means to solve the problem]

In the microcomputer according to the present invention, one of a pair of registers that can be accessed at the same time has a function of controlling whether or not to write to each bit of the corresponding register.

[Effect]

The microcomputer in this invention has registers that can be accessed simultaneously, and one register can specify whether or not to enable or disable writing to the other register in a bit-based manner, so bit operations can be performed by just writing to two registers once. becomes.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a microcomputer according to an embodiment of the present invention. In this embodiment, the microcomputer uses 4 bits as the minimum unit of data and can access 8 bits simultaneously. They are a pair of accessible registers, and 1 is an A register that controls write inhibition or permission of register 2, and this function is realized by a decoder and a mask circuit (not shown).

Further, 2 is a B register whose writing is controlled by the contents of A register l. Note that 3 in the figure indicates that the bits of registers 1 and 2 correspond to each other.

Next, the operation of the above embodiment will be explained.

For example, if a certain bit in A register 1 is "1", writing to the bit in B register 2 corresponding to that bit is permitted, and conversely, if it is "O", writing is permitted.Here, Assume that the initial values of both A register 1 and B register 2 are 'OHJ.If you write "5FH" to both registers at the same time, B register 2 becomes A register 1.
Writing to the bit set to "1" is prohibited by "5M" set to , and the initial value remains "0", and writing to the bit set to r□ is permitted. , the initial value "0" is rewritten to "1".

Therefore, the value of B register 2 finally becomes "AM".

In this way, according to this embodiment, one of a pair of registers that can be accessed simultaneously has the function of inhibiting or permitting writing to the corresponding bit of the other register. Bit operations can be performed simply by writing the required data into the memory, eliminating the overhead that was a problem with conventional read-modify-write operations.

Although the above embodiment has been explained using an 8-bit microcomputer as an example, other bit lengths may be used and the same effects as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the microcomputer of the present invention, one of the registers that can be accessed at the same time has the function of controlling the writing of the other register in a bit-based manner, so that bit operations can be processed without overhead. This has the effect of making it possible to manipulate bits by just writing to two registers once.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a register configuration of a microcomputer according to an embodiment of the present invention, and FIG. 2 is a diagram showing a flowchart of bit operations in a conventional microcomputer. In the figure, 1 is the A register, 2 is the B register, and 3 is the A register.
The bit correspondence between register 1 and B register 2 is shown. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A microcomputer having a pair of registers that can be accessed simultaneously, characterized in that one of the pair of registers is provided with means for controlling write inhibition or permission for each bit of the corresponding other register. microcomputer.