Computer graphics processing and selective visual display system – Computer graphic processing system
Reexamination Certificate
1996-10-11
2002-10-15
Tung, Kee M. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphic processing system
C345S545000, C345S554000
Reexamination Certificate
active
06466216
ABSTRACT:
TECHNOLOGY
The invention covers a computer system with an optimized controller for the display unit of the computer system. The invention further covers a process of optimized access to the display memory of a computer system as well as the use of means of sequencing memory access in a computer system for the sequencing of memory accesses to the display memory of a computer system. The invention can be applied to the control of display units in a multitude of computer systems particularly for the screen control of computer systems which are relatively small and cheap yet powerful and robust, such as mobile applications.
CURRENT TECHNOLOGY
Current technology has control facilities for the display unit of a computer system with connections to a first, primary bus system, as well as connections to a second, secondary bus system. These control facilities for the display unit of a computer system are also frequently called DISPLAY or VIDEO controllers.
The first, primary bus system has a special address and data bus. Using this primary bus system, the control facility controls for the display unit the necessary refresh cycle of the display memory using random access architecture (DRAM, dynamic random access memory), which is also frequently known as VIDEO memory.
The second, secondary bus system also has an address and data bus which connects the control facility for the display unit with the central control unit of the computer system, which is also frequently called the CPU (central processing unit). New display information which has been analysed by the central control unit is written in the display memory via this secondary bus system and/or display data is read from the display memory for current calculations in the central control unit.
Each of the bus systems has a data bus, an address bus and a control bus. These buses can be basically implemented as both bit parallel buses and as bit serial buses. Generally, these bus systems are implemented as bit parallel buses due to the transmission performance required.
Both of these independent bus systems are required to prevent access conflict to the display memory of the central control unit on the one hand, and of the control facility for the display unit on the other. Different CPU and microprocessor families have components which initialise the control facility function for the display unit, such as the VIDEO controller MC 6845 by MOTOROLA from the 6800 microprocessor family, or the VIDEO controller 8275 by INTEL from the 8080 microprocessor family.
In the book by U. Tietze and C. Schenk “Semi-conductor switching technology” (“Halbleiter-Schaltungstechnik”), Springer-Verlag, 5th edition, 1990, Berlin-Heidelberg-New York, on pages 526 to 593, the components of a microcomputer system and its functional interfaces are explained. In addition to the block diagram of a microcomputer on page 527, FIG. 21.1, the FIG. 21.54 on page 588 in particular shows an overview of microcomputer peripheral connections such as, for example, the VIDEO controller. These peripheral connections are normally accommodated on the computer system board or on a special push-in card.
Disadvantages of the Current Technology
VIDEO controller components have a large number of connections, particularly bus line connections, due to the bus architecture having a first, primary bus system and a second, secondary bus system. The number of electrical connections, which are often called pins in integrated circuits, have a considerable effect on the manufacturing costs of a component. This large number of electrical connections therefore increases the manufacturing costs of a VIDEO controller.
In addition, electrical components and the associated electrical contacts are frequently a cause of faults in an electrical system, as the electrical contacts do not have sufficiently long-term stability due to dirt, mechanical stress, corrosion, material fatigue and contact erosion, etc. The number of electrical contacts has, therefore, a considerable effect on the functional security of an electrical system. Thus a large number of electrical contacts increases the susceptibility to faults of a VIDEO controller.
In addition, the requirement of having two bus systems means considerable expenditure due to material costs and the installation costs of the second bus system. In addition, a second bus, system requires additional space, both on a board in the computer system and also in the housing of the computer system.
Task
The invention is based on the task of developing a VIDEO controller which requires a low number of electrical contacts.
Solution to the Task
This task is solved by the invention through a device which has the characteristics shown in Claim
1
.
There are advantages in that through the connection of the central control unit, the control facility for the display unit and the display memory to the common system bus only one bus system is required, and all electrical connections which were required for the primary bus system under current levels of technology no longer apply. In this way, there is a significant and advantageous reduction in the number of electrical connections on the control facility for the display unit. This means not only an advantage in costs but also the advantage of increased reliability in the computer system.
There are further advantages in that a complete bus system can be saved, which again means cost advantages for the computer system through savings in material costs and installation costs for the second bus system. In addition, there is an advantage in saving a complete bus system in that space is saved on the board of the computer system as well as in the computer system housing, which will make the computer smaller and lighter.
Yet another advantage is that in addition to a bus system, the associated driver blocks and buffer blocks can also be saved, which means not only a reduction in costs but also a lower consumption of energy.
Another advantage is that through the means of sequencing memory accesses, correct and valid access to the display memory, and in particular data integrity is guaranteed. These means of sequencing memory accesses make sure that only one component of the computer, the central control unit or the control facility for the display unit, can access the display memory. Thus collisions in memory access are advantageously avoided. The components which can access the display memory use the system bus for this.
The central control unit of the computer can be a CPU (central processing unit), a microprocessor or a microcontroller, for example. The display unit can be a cathode-ray tube, an active or passive liquid crystal display, a gas plasma panel, a field emitting cathode display or any other display facility.
The means of sequencing the memory accesses can, for example, be realised using separate control lines, which connect the components which want to access the system bus to the central control facility. Each time a component wants to access the bus, it sends a signal via the separate control line and in this way requests the right-to-access the bus (BUS REQUEST). The bus access is released by another signal (BUS RELEASE). These separate control lines can be designed as open common collectors or as open common drains.
In a similar way, the means of sequencing the memory accesses can be realised through a design which touches on the process of direct memory access (DMA) or on multi-master bus design. These designs are described in the current state of technology above (U. Tietze and C. Schenk: “Semi conductor switching technology” (“Halbleiter-Schaltungstechnik”), Springer-Verlag, 5th edition, 1990, Berlin-Heidelberg-New York).
In addition, other means of sequencing memory access is possible, such as right-to-access using a token procedure linked with an electronic token, the possession of which gives the right of access, or through a central control unit which distributes bus access, or through a hierarchical structure of components with regard to the right-of-access to the bus, with bus access issued according to
Gotze Volkmar
Neumann Martin
Bracewell & Patterson LLP
International Business Machines - Corporation
Ng Antony P.
Tung Kee M.
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