Pseudo static random access memory and control method thereof

Patent metadata

Field	Value
Publication number	US-10665286-B2
Application number	US-201816177461-A
Country	US
Kind code	B2
Filing date	Nov 1, 2018
Priority date	Feb 1, 2018
Publication date	May 26, 2020
Grant date	May 26, 2020

Abstract

In a control method, external data input to the pseudo static random access memory with a reference clock signal in a write operation are counted to generate a first count value. Data written to a dynamic memory array of the pseudo static random access memory with a built-in clock signal in the write operation are counted to generate a second count value. An initial cycle of the built-in clock signal is smaller than a cycle of the reference clock signal. The first count value is compared with the second count value. When the first count value is equal to the second count value, a write match signal is enabled. When the enabled write match signal is received, the write operation is converted from an asynchronous mode to a synchronous mode to adjust the cycle of the built-in clock signal to be equal to the cycle of the reference clock signal.

First claim

What is claimed is:

1. A control method adapted for a pseudo static random access memory, comprising:
in a write operation, counting data input to the pseudo static random access memory from external with a reference clock signal to generate a first count value;
in the write operation, counting data written to a dynamic memory array of the pseudo static random access memory with a built-in clock signal to generate a second count value, an initial cycle of the built-in clock signal is smaller than a cycle of the reference clock signal;
comparing the first count value and the second count value, when the first count value is equal to the second count value, enabling a write match signal; and
when the enabled write match signal is received, converting the write operation from an asynchronous mode to a synchronous mode to adjust the cycle of the built-in clock signal to be equal to the cycle of the reference clock signal.

2. The control method according to claim 1 , further comprising:
receiving a chip enable signal from external; and
when the chip enable signal is enabled, determining whether to perform the write operation or a read operation according to a received command,
the step of determining whether to perform the write operation or the read operation comprises:
before performing the write operation or the read operation, determining whether a refresh request is received or not; and
if the refresh request is received, performing a refresh action.

3. The control method according to claim 2 , wherein after the step of enabling the write match signal, the control method further comprises:
detecting whether the chip enable signal is disabled or not; and
if the chip enable signal is disabled, performing a pre-charge action.

4. The control method according to claim 1 , wherein converting the write operation from the asynchronous mode to the synchronous mode to adjust the cycle of the built-in clock signal to be equal to the cycle of the reference clock signal comprises:
providing a delay ready signal;
in the write operation, when the write match signal is enabled, enabling a synchronous determine signal;
when the delay ready signal is enabled and the synchronous determine signal is not enabled, generating an asynchronous base signal;
when the synchronous determine signal is enabled, generating a corresponding synchronous base signal reflecting the reference clock signal;
when in the asynchronous mode, generating the corresponding built-in clock signal reflecting the asynchronous base signal, when in the synchronous mode, generating the corresponding built-in clock signal reflecting the synchronous base signal; and
receiving the built-in clock signal and generating a control signal reflecting the built-in clock signal after a predetermined delay time.

5. The control method according to claim 2 , further comprising:
in the read operation, reading data of the dynamic memory array with the built-in clock signal, wherein the cycle of the built-in clock signal is equal to the cycle of the reference clock signal.

6. A pseudo static random access memory, comprising:
a dynamic memory array;
a controller coupled to the dynamic memory array; and
an input output circuit, coupled to the dynamic memory array and the controller, wherein
the controller comprises:
a first counter, in a write operation, the first counter counting data input to the pseudo static random access memory from external with a reference clock signal to generate a first count value;
a second counter, in the write operation, the second counter counting data written to the dynamic memory array with a built-in clock signal to generate a second count value, an initial cycle of the built-in clock signal is smaller than a cycle of the reference clock signal;
a comparer coupled to the first counter and the second counter, the comparer comparing the first count value and the second count value and, when the first count value is equal to the second count value, enabling a write match signal; and
an address strobe clock generator coupled to the comparer, when the enabled write match signal is received, the address strobe clock generator converting the write operation from an asynchronous mode to a synchronous mode to adjust the cycle of the built-in clock signal to be equal to the cycle of the reference clock signal.

7. The pseudo static random access memory according to claim 6 , wherein the controller further comprises:
an input command decoder coupled to the dynamic memory array, the input output circuit and the address strobe clock generator, the input command decoder receiving a chip enable signal from external and, when the chip enable signal is enabled, determining whether to perform the write operation or a read operation according to a received command,
before performing the write operation or the read operation, the input command decoder determines whether a refresh request is received or not and, if the refresh request is received, performs a refresh action.

8. The pseudo static random access memory according to claim 7 , further comprising:
a pre-charge control circuit coupled to the input command decoder and the comparer, during performing the write operation or the read operation, the pre-charge control circuit detecting whether the chip enable signal is disabled or not and, if the chip enable signal is disabled, performing a pre-charge action, wherein
after determining whether to perform the write operation or a read operation, the input command decoder generates an operation signal corresponding to the performed operation and a delay ready signal,
the address strobe clock generator comprises:
a synchronous controller receiving the operation signal and the write match signal and, in the write operation, when the write match signal is enabled, enabling a synchronous determine signal;
an asynchronous clock controller receiving the delay ready signal, the synchronous determine signal and the built-in clock signal and, when the delay ready signal is enabled and the synchronous determine signal is not enabled, generating an asynchronous base signal;
a synchronous clock controller receiving the reference clock signal and the synchronous determine signal, when the synchronous determine signal is enabled, generating a corresponding synchronous base signal reflecting the reference clock signal; and
a single-shot pulse generator, receiving the asynchronous base signal, the synchronous base signal and the delay ready signal and, when in the asynchronous mode, generating the corresponding built-in clock signal reflecting the asynchronous base signal, when in the synchronous mode, generating the corresponding built-in clock signal reflecting the synchronous base signal.

9. The pseudo static random access memory according to claim 8 , the address strobe clock generator further comprising:
a clock adjuster coupled to the single-shot pulse generator, receiving the built-in clock signal and generating a control signal reflecting the built-in clock signal after a predetermined delay time.

10. The pseudo static random access memory according to claim 9 , wherein in the read operation, the input output circuit reads data of the dynamic memory array with the built-in clock signal, wherein the cycle of the built-in clock signal is equal to the cycle of the reference clock signal.

Assignees

• Winbond Electronics Corp
• Windbond Electronics Corp

Inventors

• Mori Kaoru
• Ikeda Hitoshi

Classifications

• G11C7/1045

  Read-write mode select circuits · CPC title

• G11C11/40615 Primary

  Internal triggering or timing of refresh, e.g. hidden refresh, self refresh, pseudo-SRAMs · CPC title

• G11C2211/4065

  Low level details of refresh operations · CPC title

• G11C11/413

  Auxiliary circuits, e.g. for addressing, decoding, driving, writing, sensing, timing or power reduction · CPC title

• G11C11/409

  Read-write [R-W] circuits · CPC title