Static information storage and retrieval – Read/write circuit – Having particular data buffer or latch
Reexamination Certificate
1995-06-07
2001-07-03
Zarabian, A. (Department: 2824)
Static information storage and retrieval
Read/write circuit
Having particular data buffer or latch
C365S230080
Reexamination Certificate
active
06256233
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates in general to the field of electronic devices, and more particularly to a device for use in a system with distributed buffering and a method for using same.
BACKGROUND OF THE INVENTION
In electronic systems, it is often desirable to provide arrays of devices assembled to form systems or subsystems. Typical arrays are composed of DRAM, SRAM, ROM, PROM or other memory devices. Access and control to the individual devices within these arrays are established by signals which contain the necessary information to access a particular device within the array of devices. In order to maintain proper control and access of the devices within the array, it is often necessary to buffer the control signals before they are applied to the devices in the array.
Past approaches to providing the necessary buffers for array control signals include using a separate buffering device for each of the control signals required. Therefore, if the control signal is comprised of N individual signals then the array would require a buffering device for each of the N signals in the control signal. This adds devices to the array which require board space and power.
Also, if field installation of additional banks to the array is desired, i.e. field expansion of memory size, then buffers for each potential expansion bank must be included in the base assembly. For example, if the base array includes only bank zero, designing the system to accommodate the field installation of banks 1-7, requires including buffers for each of the potential expansion banks 1-7, even though the expansion buffers are not in the base system. This makes the base array larger and more expensive than necessary for its initial application.
Providing proper drive current for the control signals in an array is sometimes also needed in an array. For example, in DRAM memory systems with multiple banks of devices, drivers are required for the address, mode, row-address-strobe (RAS), and column-address-strobe (CAS) inputs. Each DRAM device and its associated interconnecting printed wiring circuit presents capacitance to each signal input. For proper DRAM function each input signal must be driven with a fast and strong driver to charge and discharge the total line capacitance in a short time. Large DRAM arrays require redundant, high speed, high power drivers to achieve acceptable performance.
The traditional solution of using discrete buffers to buffer signals in arrays has numerous disadvantages. The individual discrete buffers occupy board space, and consume power and therefore generate localized heat buildup in the system. Discrete buffers in arrays with many signals buffered in the array also produce large localized power and ground current spikes when simultaneously switching. The additional signal conductor lengths required in the printed circuit board to route the signals to the buffers adds capacitance to the signal path. In systems with expansion capability, the additional buffers must be included in the original base system. Therefore, the base system includes additional buffers that are unnecessary to its initial operation adding to the cost of the base unit. Finally, including separate discrete buffers in the array adds to the array's cost.
SUMMARY OF THE INVENTION
Accordingly, a need has arisen for a device which includes an independent buffer for buffering signals in an array of devices. In accordance with the present invention, a device with an independent buffer is provided which substantially eliminates or reduces disadvantages and problems associated with prior devices.
The device includes functional circuitry for performing a desired function. The device also contains buffering circuitry which is independent from the functional circuitry, and the buffering circuitry can be used to buffer a signal. More specifically, the device of the present invention can be used in aggregate to form a system with distributed buffering. In such a system, an array of devices of the present invention are organized into banks of devices, e.g., a memory bank for providing data storage. Access and control of the individual devices within the array are achieved with control signals. The control signals are necessarily comprised of multiple bits of information. The number of bits required is a function of the number of devices within the array. In a distributed system using the device of the present invention, each bank in the array has a unique bank input bus to transmit buffered control signals from the buffers of the individual devices to the functional inputs of the devices. The unique bank input bus is formed of the combination of the outputs of the independent buffers from each device in the bank.
This invention provides several technical advantages over the traditional solution of using discrete buffers to buffer signals in arrays. Including the independent buffer within a device adds two pins to the device, but the increase is well within currently available packaging capabilities. Another technical advantage of the present invention is that it provides the independent buffering circuitry without substantially increasing the power consumption of the device.
Using the device of the present invention with independent buffering circuitry has several technical advantages when the device is used in an array of devices. Using the device of the present invention distributes the heat generated by the buffer throughout the array thereby eliminating localized heat buildup that occurs with using discrete buffers in an array system. Another technical advantage of the present invention in array applications is the reduction of localized power and ground transients by locating only one buffer in each array device. In array applications, including buffers within the array devices provides a technical advantage of simplifying array signal routing. Shorter signal conductor lengths in an array results in better performance of the array.
Including the individual buffers on the devices of the present invention in an array of devices provides a technical advantage of facilitating expansion of the array. Since each bank within an array provides its own buffering to the individual devices within the bank, the need to provide discrete buffers in the base system in anticipation of later expansion is eliminated. These technical advantages are achieved without using discrete buffering devices that require additional power and board space in an array of devices.
REFERENCES:
patent: 3868657 (1975-02-01), Hoffman et al.
patent: 4110639 (1978-08-01), Redwine
patent: 5134583 (1992-07-01), Matsuo et al.
Brady III Wade James
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
Zarabian A.
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