JPS6283786A - Screen memory data writing system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] The present invention provides a method for inserting data from a desired bit position in a screen memory that stores data in bytes or words under the control of a processing unit (CPU). Controls input position information, rotates the bit shift number in the byte or word of the corresponding address with a ring shift counter, and sends the rotated data to the byte or word corresponding to the bit position of the screen memory. be. This enables high-speed filling, compared to the conventional method where a desired bit position is set by shifting one bit.

[Industrial application field]

The present invention relates to a screen memory data writing method for writing υ data to a desired bit position of a screen memory in units of bytes or words.

[Conventional technology]

Conventionally, as shown in the conventional screen memory 1 shown in FIG. 6, a system has been frequently used in which bytes (8 bits) or words (16 bits) 2 are accessed at once for one display time.

In this case, since addresses are assigned in units of bytes or words, there is no problem when writing, reading and displaying in units of this unit.

[Problem that the invention seeks to solve]

On the other hand, if you want to insert the filling data from a desired bit position, for example, if you want to insert it into the bit shift position ■ of word 2' in (α) of the same figure, the operation flowchart shown in (b) of the same figure shows I have to take it in hand. That is, after the CPU reads a byte or word of data, the write section is set to "O", that is, masked, and the write data is shifted so that it matches a desired bit position. Then, the logical sum (0) of the previously remaining read data and the shifted write data is read into the write area of the screen memory.

Although the above procedure can be realized using software, the main part of the procedure shown in FIG.

In the same N (C), under the control of the processing unit (CPU) 2, byte or word write data is temporarily stored in the shift register 5 from the outside via the main bus 3, and then transferred to the shift register 5 according to a command from the CPU 2. The clock generation circuit 6 applies the υ clock to the shift register 5, and sends the contents to the bit mask/bit set circuit 8 to control the storage bit position. That is, in the circuit 8, the write section is set to 0' under control from the gate control 7 in accordance with the shift clock.
mask (do not write) a predetermined number of bits, and set (write) from a predetermined bit position. This step is 1
The bits are shifted sequentially. In this way,
The set write data is transferred to the register 9 and written to the screen memory 1.

With this method, f! is masked and shifted by a predetermined number of bits! : After returning I&, the complicated procedure was to write to one pit from a predetermined bit position.

An object of the present invention is to provide a screen memory data writing method that allows data to be written to a desired bit position of a screen memory automatically and continuously from that bit position by inputting the desired bit position information. It is in.

[Means for solving problems]

In order to achieve the above object, in the present invention, when it is desired to write all data from a desired bit position of a screen memory that stores data in units of bytes or words, the desired bit position information is input and the bits of the corresponding byte or word are written. a ring shift counter that receives write data and rotates the data according to the bit shift number; Only writeable bits are written to the word.

[For production]

With the above configuration, the desired bit position information is input, the number of bit shifts within the bus or word specified by the corresponding address is rotated by the ring shift counter, the screen memory is accessed, and the desired bit is automatically It is possible to continuously write data from a certain position. As a result, it is possible to perform high-speed recombination compared to the conventional method of shifting one bit at a time.

〔Example〕

FIG. 1 is an explanatory diagram of the configuration of an embodiment of the present invention.

In the figure, under the control of a processing unit (CPU) 2, word (16 bits) write data is input from the outside via a main bus 3 to a data register 11, and write coordinates (bit positions) are input to a write coordinate register. 12 is temporarily stored.

Then, the write data of the first address is sent to the ring shift counter 13. Correspondingly, the write coordinates are sent to the bit position information generation circuit 14, which generates the word address to which the write coordinates belong and the number of bit shifts to the designated bit position.This shift clock is sent to the ring shift counter 16, and the corresponding write Include data to specified bit position P! Rotate to i.

-10,000, the designated bit position from the bit position information generation circuit 14 is sent to the write control circuit 15. The data rotated by the ring shift counter 16 is sent to the screen memory 1, and the write control circuit 15 controls writing to the υ paste part, so that only writable bits are written. Thereafter, data that has not been written to the writing section is shifted to the next address position by a ring shift counter so that continuous writing can be performed. Then repeat the same procedure as above.

FIG. 2 is an explanatory diagram of the operation of the bit shift counter, which is a main part of the embodiment shown in FIG.

For simplicity, when applying to data in units of bytes (8 bits), a double 16-bit shift counter is provided to enable circulation. When initial data is set, it is set to &9 to AI6 as indicated by the Δ mark. Then, using the shift clock of the bit position information generating circuit 14, 4 bits are shifted from the beginning and set in the grave 15 to black 16 as shown by the writable bit 0 mark. Thereafter, the data is stored cyclically in M1 to M1, and is used together with the next 4 bits of write data indicated by the X mark to write the byte of the next address.

〔Effect of the invention〕

As explained above, according to the present invention, when you want to write data to a desired bit position of a screen memory that stores data in units of bytes or words, you can input the desired bit position information and write the byte at the corresponding address. Or rotate by a bit shift number tV counting counter in a word,
The rotated data is controlled to be sent to the byte or word corresponding to the bit position of the screen memory.

This allows the number of bit shifts within a υ byte or word to be automatically set by hardware, which eliminates the conventional procedure of repeatedly shifting one bit, making it easier to achieve higher speeds. It is what it is.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the configuration of an embodiment of the present invention, Fig. 2 is an explanatory diagram of a ring shift counter, and Figs. 3 (a) to (c) are explanatory diagrams of a conventional example. Memory, 10 is CP
11 is a data register, 12 is a write coordinate register, 16 is a ring shift counter, 14 is a bit position information generation circuit, and 15 is a write control circuit.

Claims (1)

[Claims] In the screen memory data writing method that writes data from a desired bit position in a screen memory that stores data in bytes or words, input the desired bit position information and shift the number of bits to the bit position of the corresponding byte or word. and a ring shift counter that receives write data and rotates the data according to the number of bit shifts from the bit shift number generating means, and the rotated data corresponds to the bit position of the screen memory. A screen memory data writing method characterized by writing only the writeable bits sent to the byte or word to be sent, and controlling so that subsequent writing is performed continuously.