Pulse or digital communications – Cable systems and components
Reexamination Certificate
1998-04-20
2001-02-06
Tse, Young T. (Department: 2734)
Pulse or digital communications
Cable systems and components
C370S364000, C326S020000
Reexamination Certificate
active
06185256
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a transmission system, a receiver circuit for use in the transmission system, and a semiconductor memory device to which the signal transmission system is applied, and more particularly to a transmission system using a PRD (partial response detection) method, a receiver circuit for use in the signal transmission system, and a semiconductor memory device to which the signal transmission system is applied.
2. Description of the Related Art
In recent years, with advances in semiconductor technology, the speed of processors (MPUs: Micro Processor Units) has increased dramatically. The performance of semiconductor memory devices, exemplified by DRAMs (Dynamic Random Access Memories), has also improved to some extent in terms of speed, but compared with the increase in processor speed, the disparity has been growing steadily.
Stated another way, processor performance has increased dramatically in terms of speed, whereas DRAM performance improvements have been dramatic primarily in terms of storage capacity. However, DRAM speed improvements have not been so dramatic as the increase in storage capacity, as a result of which the gap between the speed of DRAMs and that of processors has widened and this speed gap has become a bottleneck in boosting system (computer) performance in recent years. Furthermore, as chip sizes increase, the speed of signal transfers between devices and between constituent circuits within one LSI chip (semiconductor memory) is becoming a major limiting factor in chip performance.
If this situation continues, a situation may arise where the overall system speed cannot increase at all despite increased processor speed, eventually leading to stagnation of the information industry. There is therefore a growing need to increase the speed of semiconductor memory devices and, particularly, the data transfer speed in semiconductor memory devices.
The prior art and problems associated with the prior art will be described in detail later with reference to drawings.
SUMMARY OF THE INVENTION
A primary object of the present invention is to improve the overall speed of semiconductor memory devices by making continuous (seamless) column reads possible while increasing not only readout but also write speeds.
According to the present invention, there is provided a signal transmission system for transmitting data over a signal transmission line without requiring precharging the signal transmission line for every bit, by eliminating an intersymbol interference component introduced by preceding data, wherein the signal transmission line comprises a plurality of switchable signal transmission lines organized in a branching structure or a hierarchical structure, at least one target unit from which to read data is connected to each of the plurality of signal transmission lines, and a readout circuit including a circuit for eliminating the intersymbol interference component is connected to the signal transmission line, and the intersymbol interference component elimination circuit reduces noise introduced when the signal transmission line is switched between the plurality of signal transmission lines, and thereby provides a smooth intersymbol interference component elimination operation when the signal transmission line is switched.
The response time of the signal transmission line may be set approximately equal to or longer than the length of a transmitted symbol. When transferring continuous data from the same signal transmission line, precharging of the signal transmission line for every bit may not be performed, and during a period preceding the switching of the transmission line and during a period when continuous data transmission is not performed, some of the plurality of signal transmission lines may be precharged to a predetermined voltage level. When the signal transmission line is switched from a first signal transmission line to a second signal transmission line, the second signal transmission line to be selected next may be precharged to a predetermined voltage level before the signal transmission line is switched.
The readout circuit may be a circuit employing a partial-response detection method, and the readout circuit employing the partial-response detection method may correct the intersymbol interference component elimination, when the signal transmission line is switched, by varying an input capacitance value. The readout circuit employing the partial-response detection method may include an intersymbol interference estimation unit for estimating intersymbol interference from a previously received signal; and a decision unit for making a logic decision on a currently received signal by subtracting the estimated intersymbol interference from the currently received signal. The readout circuit employing the partial-response detection method may include first and second partial-response detection amplifiers, arranged in parallel with each other, wherein the first partial-response amplifier may perform an intersymbol interference estimation operation while the second partial-response detection amplifier is performing a data decision operation and, at the next timing, may perform a data decision operation while the second partial-response detection amplifier is performing an intersymbol interference estimation operation.
The signal transmission line may be configured as complementary buses and the readout circuit may be configured as a complementary-type bus amplifier. The readout circuit may operate only when data is transferred via the signal transmission line. When the signal transmission line is switched, a first driver select signal for selecting a driver on an activated signal transmission line currently transmitting data thereon and a second driver select signal for selecting a driver on a signal transmission line currently inactive and expected to be activated after the switching may be generated as a common driver select signal, and the inactive signal transmission line may be precharged during a period that includes the last cycle of the state in which data in an arbitrary driver on the inactive signal transmission line, selected simultaneously when selecting a driver on the activated signal transmission line, may be transmitted on the inactive signal transmission line. The common driver select signal may be also supplied in common to the plurality of signal transmission lines other than the signal transmission line expected to be activated next.
A timing signal for carrying out the switching of the signal transmission line may be generated externally and distributed to a switching circuit for each signal transmission line, or may be supplied at timing before the last one cycle of amplification of a currently activated signal transmission line. Before switching the signal transmission line an inactive signal transmission line may be precharged in such a direction as to reduce the noise that has an effect on an intersymbol interference component elimination operation subsequently performed in the readout circuit, or may be precharged to a voltage level within a range of plus or minus a predetermined voltage about a voltage at one half of either a read or write maximum amplitude of the signal transmission line, the predetermined voltage being smaller than a transistor threshold voltage.
According to the present invention, there is also provided a signal transmission system for transmitting data over a signal transmission line without requiring precharging the signal transmission line for every bit, by eliminating an intersymbol interference component introduced by preceding data, wherein the signal transmission line comprises a plurality of switchable transmission lines, and when the signal transmission line is switched from a first transmission line to a second transmission line, the second transmission line to be selected next is precharged to a predetermined level before switching the signal transmission line, in order to continue data transmission.
The signal transmission s
Ogawa Junji
Saito Miyoshi
Arent Fox Kintner & Plotkin & Kahn, PLLC
Fujitsu Limited
Tse Young T.
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