JPS63206872A - Picture memory - Google Patents

Abstract

PURPOSE:To quickly access a window by providing window area start and end address holding means, counters, comparing means, etc., to reduce the burden on software. CONSTITUTION:The start address is set to a register 4 and a counter of the window area start address holding means, and the end address is set to registers 6 and 7. The increment address from a counter 8 and the address from the counter 5 are processed in comparators 12a and 12b through a selector 9: and when the increment address coincides with contents of the register 6, contents of the register 4 are set to the counter 8 again through a controller 13 and contents of the counter 5 are incremented by +1. A CPU 1 repeats the same operation to access a window area of a RAM 10 with only setting of start and end addresses. Meanwhile, addresses other than the address of the window area from the CPU 1 and an I/O 13 are inhibited by comparators 11a, 11b, 12a, and 12b, and the burden on software is reduced in any case to quickly access the window.

Description

[Detailed description of the invention] The present invention relates to an image storage device having an image access function.

(Prior Art) In a conventional image storage device, a CPU controls an address counter that controls the address of an image memory. In other words, address control is performed by software.

However, in such a configuration, when a rectangular window area of an arbitrary size is set in the image memory and the window area is accessed, a large burden is placed on the software.

Another drawback of such software-based access control is that the access speed is slow.

(Problems to be Solved by the Invention) As described above, conventional image storage devices have the problem that window access places a burden on the software and the access speed is slow.

The present invention aims to provide an image storage device that reduces the burden on software and further speeds up window access by realizing a window access function in hardware, and a window area that is set. window address holding means for holding the start address counter and end address data of the image memory; and address data output from the address counter that controls the address of the image memory and address data supplied from the control bus to be selectively taken out. a first selection means for comparing the address data output from the address counter and the address data supplied from the control bus;
a second comparison means for comparing the address data retrieved by the selection means with the end address data; and a second comparison means for comparing the address data retrieved by the selection means with the end address data, and the content of the address counter is changed to the start address based on the comparison results of the first and second comparison means. means for incrementing the initial value until it matches the end address, and when the selection means selects the address data from the control bus, the address data from the control bus is incremented based on the comparison results of the first and second comparison means. The present invention is characterized by providing means for prohibiting access to the image memory by the address data when the address data corresponds to an address outside the window area.

The start address data held in the window address holding means is incremented as an initial value, and when it matches the end address data held in the window address holding means, the access ends. As a result, among the contents of the image memory, only the data in the window area given by the start and end address data held in the window address holding means is accessed.

On the other hand, when accessing the image memory using address data from an external CPU, etc. input from the control bus, such as when performing affine transformation etc. using software, the address data is accessed using the start and end address data of the window area. It is determined whether the data corresponds to an address within the window area, and if it is recognized as data outside the window area, access to the image memory by that address data is prohibited.

(Embodiment) FIG. 1 is a block diagram of an image storage device according to an embodiment of the present invention. In the same figure, register 4°, that is, X in the window area indicated by diagonal lines in FIG.

Holds X-direction start address data Xs, Ys and end address data Xe, Ye.

The contents of the register 4 holding the X-direction start address data Xs of the window area are input to the X-direction address counter 8 as an initial value. The counter 5 that holds the start address data Ys in the X direction of the window area is
It also serves as a direction address counter (hereinafter, counter 5 will be referred to as an address counter).

The address data (Xl, Yj) from the X-direction and X-direction address counters 8.5 are applied to one input of the selector 9. The other input of the selector 9 is given address data input from the CPUI via the control bus 2 and interface 3.

The address data selected by the selector 9 is supplied to the image memory 10. The image memory 10 is composed of a RAM, and for example, as shown in FIG.
It has an address space of In addition, address data Xi, Yj from the image memo address counters 8, 5
are the comparators ll and ll as the first comparison means, respectively.
It is given to one input of a and llb. comparator l
Address data input from the CPU via the control bus 2 and interface 3 is applied to the other inputs of la and llb.

On the other hand, the address data selected by the selector 9 is
Each of the signals is applied to one input of comparators 12a and 12b, which are second comparison means. Comparator 12a,
12b has the end address data Xe in the x and X directions of the window area held in the register 6.7.
, Yc are given, respectively.

Comparators lla, llb and 12a.

The comparison result 12b is manually input to the controller 13.

Controller 13 controls address counters 8, 5 and image memory 10 based on these comparison results. Further, the controller 13 is used to switch between the select control bus 2 and the select control bus 2.

Next, the operation of the image storage device of this embodiment will be explained. The window access function of this device is (1)
(2) When accessing the image memory 10 from the CPUI, access to addresses outside the window area is prohibited and only access within the window area is allowed. There is window access.

When accessing the window in (1), first, the start address data Xs in the X direction of the window area is stored in the register 4 from the CPU via the control bus 2 and interface 3.
However, the start address data Ys in the X direction is stored in the address counter 5, and the end address data Ys in the X direction is stored in the register 61;
e and end address data Ye in the X direction are set in the register 7, respectively. Next, the contents of the register 4 are loaded into the address counter 8, and the contents of the address counter 8, that is, the address data Xt in the X direction, are transferred to the comparator 12a by the address counter 8. When it is determined that the data matches the data of the end address Xe in the X direction from the register 6, the contents of the register 4 are reloaded into the address counter 8 under the control of the controller 13, and the contents of the address counter 5, that is, the data in the X direction are reloaded. address data Yj is incremented by one. Thereafter, Yj is incremented every time Xl-Xc becomes Xl-Xa, Yj-Y
The window area in the image memory 10 is accessed by performing similar operations until reaching e.

In this case, the CPU only needs to generate the start and end address data of the window area, and there is no need to generate individual address data within the window area.
The software becomes very simple. Furthermore, since the address data can be advanced simply by incrementing the contents of the address counter 8.5, the access speed of the image memory 10 is extremely fast.

On the other hand, when accessing the window in (2), register 4 is first accessed as in (1). Address counter5. Arbitrary address data is input to the register and provided to the image memory 10 via the selector 9. The address counter input at this time is the comparator 11a.

11b, 12a, and 12b are constantly compared with window addresses, that is, Xs, Ys, Xe, and Ye. Then, the controller 13 controls the comparator ll.
If it is determined that the input address data corresponds to an address outside the window area from the comparison results of a, Access to the image memory 10 using address data is prohibited.

In this case as well, the CPU can generate address data without considering the window area, so the software for this purpose is simple.

[Effects of the Invention] According to the image storage device according to the present invention, the burden on software for window access can be greatly reduced, and the access speed can be increased.

FIG. 3 is a diagram showing the structure of address data of the image memory.

1... CPU, 2... Control bus, 3... Interface, 4... Register, 5... Address counter, 6... Register, 7... Register, 8... Address counter , 9... selector (selection means), 10
... image memory, 11a, 11b... comparator (first comparing means), 12a, 12b... comparator (second comparing means), 13... controller, 14
...Selector, 15...Data bus, 16...Interface O

Claims (1)

[Scope of Claims] An image memory for storing image data, a window address holding means for holding start address data and end address data of a window area set for the image memory, and controlling an address of the image memory. an address counter that outputs the address data outputted from the address counter and address data supplied from the control bus; selection means that selectively extracts the address data outputted from the address counter and the address data supplied from the control bus and applies the extracted address data to the image memory; a first comparing means for comparing the address data supplied from the control bus; a second comparing means for comparing the address data taken out by the selecting means and the end address data; means for incrementing the contents of the address counter with the starting address as an initial value until it matches the ending address based on the comparison result of the comparing means; and the selecting means selects the address data from the control bus. If the address data from the control bus is data corresponding to an address outside the window area, means for prohibiting access to the image memory by the address data based on the comparison results of the first and second comparison means. An image storage device comprising: