Semiconductor memory asynchronous pipeline
View Patent ↗An asynchronously pipelined SDRAM has separate pipeline stages that are controlled by asynchronous signals. Rather than using a clock signal to synchronize data at each stage, an asynchronous signal is used to latch data at every stage. The asynchronous control signals are generated within the chip and are optimized to the different latency stages. Longer latency stages require larger delays elements, while shorter latency states require shorter delay elements. The data is synchronized to the clock at the end of the read data path before being read out of the chip. Because the data has been latched at each pipeline stage, it suffers from less skew than would be seen in a conventional wave pipeline architecture. Furthermore, since the stages are independent of the system clock, the read data path can be run at any CAS latency as long as the re-synchronizing output is built to support it.
1. A semiconductor memory device comprising:
a memory core having addressable memory elements;
a plurality of pipeline stages, each pipeline stage having a latency;
a plurality of control logic and delay elements, each control logic and delay element delaying a control signal by a delay corresponding to the latency of a respective one of the plurality of pipeline stages to produce a corresponding pipeline control signal, each pipeline stage being latched by the pipeline control signal corresponding to the previous pipeline stage; and
a synchronizer responsive to a clock signal received from a delay locked loop (DLL), the synchronizer being configured to
output read data as synchronized data through an output buffer.
2. The semiconductor memory device of claim 1 , further comprising:
a signal provider for providing a latch control signal in response to the clock signal and a read signal.
3. The semiconductor memory device of claim 2 , wherein the signal provider comprises:
an enable signal provider for providing first and second enable signals as the latch control signal in response to the clock signal.
4. The semiconductor memory device of claim 3 , further comprising:
a data latch configured to:
input the directed data thereinto in response to the first enable signal, and
output the latched data as the synchronized data in response to the second enable signal.
5. The semiconductor memory device of claims 4 , wherein the signal provider further comprises:
a counter for counting the clocks of the clock signal; and
delay circuitry for delaying a count output from the counter to provide the first and second enable signals.
6. The semiconductor memory device of claim 3 , wherein the latch circuitry comprises:
a plurality of data latches coupled in parallel, the data latches being configured to
input the directed data thereinto in response to the first enable signal, and
output the latched data as the synchronized data in response to the second enable signal.
7. The semiconductor memory device of claim 6 , wherein the signal provider further comprises:
a counter for counting the cycles of the clock signal; and
delay circuitry for delaying a count output from the counter to provide the first and second enable signals.
8. The semiconductor memory device of claim 7 , wherein the signal provider further comprises:
a latch for providing the first enable signal in response to the delayed signal from the delay circuitry and a delayed signal derived from a memory control signal.
9. The semiconductor memory device of claim 1 , wherein the synchronizer comprises:
data output circuitry configured to receive the output data from the data latch and output the received data to the data output port as the synchronized data.
10. The semiconductor memory device of claim 9 , wherein the data output circuitry is further configured to synchronize data output in response to a delayed clock signal provided by the delay locked loop.
11. The semiconductor memory device of claim 9 , wherein the data output circuitry is further configured to synchronize data output in response to edges of the delay clock signal.
12. The semiconductor memory device of claim 9 , wherein the data output circuitry is further configured to synchronize data output in response to either rising edges or falling edges of the delay clock signal.
13. The semiconductor memory device of claim 9 , wherein the data output circuitry is further configured to synchronize output data in response to rising edges and falling edges of the delay clock signal.
14. The semiconductor memory device of claim 1 , further comprising a timing delay element configured to define the latency.
15. The semiconductor memory device of claim 1 , wherein the memory core comprises a dynamic random access memory.
16. The semiconductor memory device of claim 1 , further comprising latch circuitry for receiving the read data and outputting the read data to the synchronizer as latched data.
17. The semiconductor memory device of claim 16 , wherein the latch circuitry comprises a register.
18. The semiconductor memory device of claim 17 , wherein the register is a FIFO register.
19. The semiconductor memory device of claim 1 , wherein the synchronizer further comprises latch circuitry for receiving parallel read data from the memory core and outputting serialized read data through the output buffer.
20. The semiconductor memory device of claim 19 , wherein the synchronizer further comprises:
first circuitry to output data in response to a rising edge of the clock signal received from the DLL, and second circuitry to output data in response to a falling edge of the clock signal received from the DLL.
21. The semiconductor memory device of claim 19 , wherein the synchronizer further comprises:
first circuitry to receive a clock signal from the DLL and a complementary clock signal of the DLL;
second circuitry to output data in response to a rising edge of the clock signal received from the DLL, and
second circuitry to output data in response to a rising edge of the complementary clock signal received from the DLL.
22. A double data rate (DDR) synchronous dynamic random access memory (SDRAM) comprising:
a memory core having addressable memory elements;
a first path, defined between an address input port and a data output port, the memory core being included in the first path,
the first path including a plurality of pipeline stages, each of the plurality of pipeline stages including a latch responsive to a corresponding control signal;
a plurality of delay elements associated with the plurality of pipeline stages, each of the plurality of delay elements being configured to provide the corresponding control signal, the corresponding control signal being provided in response to a delayed version of a system clock signal and a command signal; and
a delay locked loop (DLL) circuit having an output for providing a DLL clock signal to a data output buffer, the data output buffer being configured to output data in response to the DLL clock signal.
23. The SDRAM of claim 22 , wherein one of the plurality of the asynchronous control signals is a gated version of the system clock signal.
24. The SDRAM of claim 23 , wherein one of the plurality of delay elements is configured to gate the delayed version of the system clock as the asynchronous control signal provided from a previous one of the plurality of delay elements.
25. A pipelined double data rate synchronous dynamic random access memory (SDRAM) comprising:
a memory core having addressable memory elements;
a first path, defined between an address input port and a data output port,
the first path comprising a data output buffer, the memory core being included in the first path,
the first path including a plurality of pipeline stages, each of the plurality of pipeline stages including a latch responsive to a corresponding control signal;
a plurality of delay elements associated with the plurality of pipeline stages, each of the plurality of delay elements being configured to provide the corresponding control signal, the corresponding control signal being provided in response to a delayed version of a system clock signal and a command signal; and
a delay locked loop (DLL) circuit having an output for providing a DLL clock signal to a data output buffer, the data output buffer being configured to output data in response to the DLL clock signal.
26. A pipelined double data rate synchronous dynamic random access memory (SDRAM) comprising:
a memory core having addressable memory elements;
a first path, defined between an address input port and a data output port,
the first path comprising at least one data output buffer, the memory core being included in the first path,
the first path including a plurality of pipeline stages, each of the plurality of pipeline stages including a latch responsive to a corresponding control signal;
a plurality of delay elements associated with the plurality of pipeline stages, each of the plurality of delay elements being configured to provide the corresponding control signal, the corresponding control signal being provided in response to a delayed version of a system clock signal; and
a delay locked loop (DLL) circuit having an output for providing a DLL clock signal to a data output buffer, the data output buffer being configured to output data in response to the DLL clock signal.