Data strobe gating
View Patent ↗Methods and devices for gating an internal data strobe from an input buffer of a memory device. The gating function occurs after a write operation ceases but before an external controller stops driving an external data strobe that is used to generate the internal data strobe. The methods and devices use local counters to count how many pulses have occurred on the data strobe during a write operation. When the local counters indicate that an expected number of cycles for the write operation have elapsed, the local counters indicate that the write operation has completed. This indication causes gating circuitry to cut off the internal data strobe from writing circuitry.
1. A memory device, comprising:
an input data strobe (DQS) buffer configured to receive a DQS signal;
gating circuitry configured to toggle a connection of the DQS signal to write circuitry using a gated signal that reflects the DQS signal when the connection is enabled; and
one or more counters configured to count cycles of the gated signal during a write operation when the connection is enabled, wherein the gating circuitry is configured to toggle the connection based at least in part on the counted cycles of the gated signal, wherein the gated signal comprises a cyclic redundancy check (CRC) when enabled in a mode register for the memory device.
2. The memory device of claim 1 , wherein the one or more counters are each configured to count each bit of the write operation.
3. The memory device of claim 2 , wherein each of the one or more counters comprises a flip flop that counts pulses on a gated version of the DQS signal by receiving the gated version of the DQS signal output from the gating circuitry, wherein the gated version of the DQS signal output is received at a clock pin of the flip flop and a counting data pulse is passed sequentially through the counters using the gated version of the DQS signal.
4. The memory device of claim 3 , wherein the gated version comprises a gated data signal (DS) that is logically equivalent to the DQS signal or a gated data signal false (DSF) that is a logical complement to the DS.
5. The memory device of claim 1 , wherein the gated signal comprises 16 bits of double-data rate (DDR) on 8 consecutive cycles of the DQS signal.
6. The memory device of claim 1 , comprising circular count circuitry that add additional cycles to the cycles when two consecutive write operations occur to quickly to reset the one or more counters.
7. The memory device of claim 1 , comprising latching circuitry that generates a gating enable signal based at least in part on the counted cycles of the write operation, wherein the gating enable signal controls operation of the gating circuitry.
8. The memory device of claim 7 , wherein the latching circuitry is configured to receive a write end (WrEnd) signal indicative of a beginning of a last cycle of the write operation to place the latching circuitry in an active mode where a next falling edge of the gated signal is configured to change the gating enable signal.
9. The memory device of claim 8 , wherein the WrEnd signal is received from a last-cycle counter of the one or more counters that is configured to count a last cycle of the write operation.
10. The memory device of claim 1 , wherein the gating circuitry is connected directly to input buffer with no logic gates therebetween.
11. A method, comprising:
receiving a DQS signal at a memory device from a controller;
gating the DQS signal with gating circuitry to produce a gated DS signal during a write operation;
counting cycles of the gated DS signal using one or more counters; and
when the counted cycles indicate that the write operation is completed, toggling the gating circuitry to cease passing the DQS signal as the gated DS signal to write circuitry, wherein toggling the gating circuitry occurs after a write operation but before the received DQS signal transitions to an indeterminate state due to the controller ceasing to drive the received DQS signal.
12. The method of claim 11 , wherein counting the cycles of the gated DS signal comprises toggling a counter of the one or more counters for each cycle of the gated DS signal during the write operation.
13. The method of claim 12 , wherein counting the cycles of the gated DS signal comprises passing the gated DS signal to a flip flop of each counter and passing a counting data pulse through the counters by connecting a data pin of the flip flop to an output pin of a previous bit counter of the one or more counters to propagate the counting data pulse through the one or more counters using the gated DS signal.
14. The method of claim 11 , wherein toggling the gating circuitry comprises:
receiving a write end (WrEnd) signal that indicates that a last cycle of the write operation has started;
in response to the WrEnd signal, placing latching circuitry in an active state;
receiving an ungated version of the DQS signal; and
when the ungated version of the DQS signal transitions high while the WrEnd signal is in the active state, disabling output of the DQS signal as the gated DS signal.
15. A memory device, comprising:
an input data strobe (DQS) buffer configured to receive a DQS signal and output a data signal (DS) and a data false signal (DSF);
first gating circuitry configured to toggle a first connection of the DS to write circuitry using a gated DS signal that reflects the DS signal when the first connection is enabled;
second gating circuitry configured to toggle a second connection of the DSF to write circuitry using a gated DSF that reflects the DSF when the second connection is enabled;
one or more counters configured to count cycles of the gated DS and the gated DSF when the first and second connections are enabled by passing a counting data pulse sequentially through the one or more counters;
first latching circuitry configured to control the first gating circuitry based at least in part on the counted cycles; and
second latching circuitry configured to control the second gating circuitry based at least in part on the counted cycles.
16. The memory device of claim 15 , wherein the one or more counters comprises pulse length circuitry configured to cause the counting data pulse to have an expected length from a write end (WrEnd).
17. The memory device of claim 16 , wherein the one or more counters comprises circular count circuitry configured to add circular count functionality when consecutive write operations are too frequent to reset the one or more counters between the consecutive write operations.
18. The memory device of claim 15 , wherein the one or more counters are configured to walkback a plurality of progressive clocks in the one or more counters having a plurality of shift register stages that each utilizes a different progressive clock of the plurality of progressive clocks to progressively increase speed for each corresponding shift register stage until a fastest clock of the plurality of progressive clocks is used on a final register stage of the plurality of shift register stages.