Integrated Silicon Solution Incorporated

Intel Corporation

Yong H Jiang

Steve W Lim

Ping Lo

A write control circuit and method for an asynchronous SRAM that minimizes the write address hold time required to prevent data from being written to incorrect addresses in the memory. The write control circuit temporarily disables a write circuit in the memory whenever the memory address changes. The delay of the write control circuit from input to output is shorter than the delay of a decoder in the memory.

Apparatus and method for minimizing address hold time in asynchronous

A self timed memory address control circuit is described. A Y address signal is pre-decoded and then latched. Address transition detection circuits coupled to X and Y address lines output a pulse to an equalization circuit whenever one of the corresponding address signals change. The WEB address detection circuit outputs a pulse when the WEB signal switches high. When the equalization circuit receives one of these pulses it generates an output pulse to an equalization transistor that is coupled between two local I/O bus lines. The equalization circuit output pulse turns on this transistor to equalize the local I/O bus lines so as to prevent data from being written with them. The equalization circuit also outputs a pulse to a clock generator circuit. The clock generator circuit generates a clock signal which clocks the latch. This causes the latch to couple the pre-decoded output signals to a decoder. The decoder then combines the pre-decoded address signals with other control signals. The decoder then activates the appropriate column select lines. Shortly thereafter the equalization pulse switches low, and a write pulse signal switches high to write data into the selected memory cell. This ensures that at the end of a write operation, when the Y address changes and WEB changes from low to high, the column select will change only after the equalization signal is asserted. The equalization pulse remains high to keep the local I/O bus lines equalized until after the write pulse has switched low. This thereby avoids the uncertainty in the matched delay requirements between the equalization signals and the decoded address signals of conventional asynchronous memory devices and prevents data from being improperly written into the memory address for the subsequent cycle.

Method and apparatus for controlling memory address hold time

A flexible memory controller capable of performing any combination of read, write and deselect operations is described. The present invention can store two pending write or read operations and perform a third write or read operation. In a ZBT SRAM embodiment the memory controller has three address registers, two data registers, and two comparators. Addresses for pending memory access operations are shifted in the address registers so that memory access addresses can be stored without overwriting the memory addresses for the pending operations. Similarly, data is shifted in the data registers to ensure that data remains available for pending memory access operations. The specific register operations are controlled by a thirteen state state machine. The thirteen states and the relationships between the states are defined to enable the memory controller to perform any combination of read, write and deselect operations without inserting idle cycles. When a read address matches the address of a pending write operation it indicates that the data that the read address is intended to retrieve has not yet been written to the memory array. The data for this read operation may be in one or more places including the memory I/O pins, either of the two data registers, or inside the memory. The state machine includes a series of logical comparisons to identify the location of the desired data. After the data location is determined the data is loaded into the output register.

System and method for a flexible memory controller

A tunable phase generator is disclosed suitable for use in integrated circuits. The phase generator includes a delay element wherein passive resistors and conductors are employed to provide relatively constant delays despite changes in operating temperatures and voltages. The phase generator is driven by a clock signal and generates therefrom a self-resettable output signal pulse with a selectable pulse width no longer than the width of the clock signal. The variable widths are provided by varying the delays of the delay elements and adding combinational logic between respective delay elements and at the input and output of the phase generator that ensure that, in most situations, the output signal pulse is reset after a delay that is independent of the pulse width of the clock signal. Delays are lengthened by decreasing the current available to a delay element for charging the capacitors. Delays are decreased by disconnecting at least some of the capacitors so that the corresponding delay element has virtually no delay.

Fuse tunable, RC-generated pulse generator

A novel address enable circuit for use in a synchronous memory that includes a memory core. The address enable circuit includes an address latching circuit that outputs a synchronized address and latches a pre-decoded address when an input clock signal transitions from a first logical level to a second logical level so that the synchronized address identifies the pre-decoded address. The address enable circuit also includes a reset circuit that generates a reset signal that (1) does not indicate a reset when the latched chip enable signal indicates that the memory has been selected while the clock signal is at the second logical level, (2) indicates a reset when the latched chip enable signal indicates that the memory has not been selected while the clock signal is at the second logical level, and (3) does not indicate a reset while the clock signal is at the first logical level. The address latching circuit is reset when the reset signal indicates a reset so that the synchronized address identifies a disabled address that indicates that memory access to the memory core is disabled and is not reset when the reset signal does not indicate a reset.

Address enable circuit in synchronous SRAM

A novel driver circuit is disclosed that is used for driving a logic voltage sensed by a sensing amplifier of a memory onto a data line of the memory. The driver circuit is responsive to first sensing signals and second sensing signals that are delayed with respect to the first sensing signals. When the first and second sensing signals indicate that equalization is occuring in the sensing amplifier, the driver circuit latches the data line logic voltage on the data line without any false transitions or glitches occuring on the data line. In addition, the driver circuit becomes self biased when the first sensing signals indicate that sensing is occuring in the sensing amplifier but the second sensing signals indicate that equalization is still occuring. This is done to minimize the voltage swing in the driver circuit when the sensed logic voltage is driven onto the data line while both the first and second sensing signals indicate that sensing is occuring.

Driver circuit for use with a sensing amplifier in a memory

A wordline wakeup circuit for use in a static memory responsive to an external clock signal and chip enable signals provided by a controller/microprocessor to perform a memory operation on the static memory. The wordline wakeup circuit receives a global clock (GCLK) signal generated by memory control circuitry from the external clock signal and a word line enable (WLEN) signal asserted by the control circuitry when the chip enables indicate a pending memory operation. The wordline wakeup circuit asserts a wordline wakeup signal (LWLEN) signal as soon as possible after the GCLK signal goes high. The LWLEN signal when asserted activates decoder circuity to assert wordlines as necessary to perform the memory operation. If the WLEN signal is provided, the wordline wakeup circuit keeps the LWLEN signal high for at least the high portion of the GCLK signal, enabling the decoder to execute the memory operation, if the WLEN signal is not provided, the wordline wakeup circuit drops the LWLEN signal. The short pulse made by the LWLEN signal when there is no pending memory operation does not affect the decoder.

Wordline wakeup circuit for use in a pulsed wordline design

A multi-location word line repair circuit is described that can be employed in a static memory including a plurality of sub-arrays responsive to respective sets of global word lines (GWL). Included in the repair circuit is a redundant word line (WL) decoder that stores and subsequently decodes the address of a defective global word line to be repaired. A selector circuit coupled to the redundant WL decoder is activated whenever the decoder decodes the stored address of the defective GWL from the memory address lines. When this occurs, the selector circuit activates at least one redundant global word line to repair the defective global word line within a selected group of global word lines that can include any combination of the respective sets of GWLs that are provided to the plurality of sub-arrays. To prevent the defective GWL from interfering with a memory operation being performed by the substitute RWL, a deselector circuit disables the defective global word line within the selected group of word lines.

Multiple location repair word line redundancy circuit

A power-on detection circuit for detecting when a supply output voltage exceeds a predetermined level. According to a present embodiment, the power-on detection circuit generally comprises a pull-up transistor, a pull-down transistor, and an inverter. The pull-up transistor and the pull-down transistor are commonly coupled to a node for biasing the node to a first voltage, and the inverter has its input coupled to receive the first voltage. The inverter indicates that the supply output voltage is less than the predetermined level when the first voltage is greater than a trip voltage of the inverter. The inverter indicates that the supply output voltage exceeds the predetermined level when the first voltage is less than the trip voltage of the inverter. According to one embodiment, a biasing circuit comprising a voltage divider is provided to bias the pull-down transistor as a function of the supply output voltage such that the gate voltage of the pull-down transistor varies at the same rate as the supply output voltage.

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Milpitas, CA, United States of America

Yong H Jiang