Semiconductor device having reset function
View Patent ↗A semiconductor device comprises a memory cell array, a row control circuit for controlling an access to the memory cell array, and a refresh control circuit for instructing the row control circuit to refresh the memory cell array. After temporarily transiting to a reset state due to an activation of a reset signal, the refresh control circuit instructs to refresh the memory cell array in response to a transition to an initial state due to a de-activation of the reset signal.
1. A semiconductor device comprising:
a memory cell array;
an access control circuit configured to access the memory cell array; and
a refresh control circuit configured to control the access control circuit so that the access control circuit is free from performing a refresh operation on the memory cell array when the semiconductor device is in a reset state, and so that the access control circuit performs the refresh operation on the memory cell array without receiving a refresh request from outside of the device when the semiconductor device transits from the reset state to an initial state.
2. The semiconductor device as claimed in claim 1 , wherein
the refresh control circuit is configured to produce a refresh signal a plurality of times, and
the access control circuit is configured to perform the refresh operation in response to each occurrence of the refresh signal.
3. The semiconductor device as claimed in claim 2 , wherein the refresh control circuit is configured to be free from producing the refresh signal when the semiconductor device is in the reset state, and produces a refresh signal after the semiconductor device transits from the reset state to the initial state.
4. The semiconductor device as claimed in claim 3 , wherein the refresh control circuit is configured to stop producing the refresh signal in response to a first exit signal.
5. The semiconductor device as claimed in claim 4 , wherein the first exit signal is a clock enable signal.
6. The semiconductor device as claimed in claim 3 , further comprising a count control circuit configured to generate a second exit signal when the refresh control circuit produces the refresh signal a first number of times,
wherein the refresh control circuit is configured to stop producing the refresh signal in response to the second exit signal.
7. The semiconductor device as claimed in claim 6 , wherein the count control circuit is configured to initialize a count value of counting the refresh signal when the second exit signal is generated.
8. A device comprising:
a memory cell array;
a reset input circuit configured to produce a reset signal that takes one of first and second logic levels;
a first control circuit configured to be free from issuing a refresh signal when the reset signal is in the first logic level and issue the refresh signal in response to a transition of the reset signal from the first logic level to the second logic level; and
a second control circuit configured to perform a refresh operation on the memory cell array in response to the refresh signal.
9. The device as claimed in claim 8 , wherein the first control circuit is configured to issue the refresh signal at least twice in response to the transition of the reset signal without receiving a refresh request from outside.
10. The device as claimed in claim 8 , wherein the first control circuit is configured to stop issuing the refresh signal at a time when a clock enable signal is activated.
11. The device as claimed in claim 8 , wherein
the first control circuit includes a first circuit unit configured to count up a count value thereof in response to the each issuance of the refresh signal and the first control circuit is configured to stop issuing the refresh signal when the count value of the first circuit unit reaches a first value.
12. A device comprising:
a memory cell array;
a control circuit configured to keep the memory cell array in a reset state during a first period of time, release the memory cell array from the reset state thereof to an initial state thereof and keep the memory cell array in the initial state during a second period of time following the first period of time, the control circuit being further configured to be free from performing a refresh operation on the memory cell array during the first period of time and perform the refresh operation on the memory cell array during the second period of time without receiving a refresh request from outside of the device.
13. The device as claimed in claim 12 , wherein the control circuit is configured to release the memory cell array from the initial state thereof to an operable state thereof after the second period of time.
14. The device as claimed in claim 12 , wherein the control circuit receives a reset signal that takes a first logic level during the first period of time and takes a second logic level during the second period of time, and the control circuit is configured to release the memory cell array from the reset state thereof to the initial state thereof in response to a transition of the reset signal from the first logic level to the second logic level.
15. The device as claimed in claim 8 , wherein the first control circuit is configured to issue the refresh signal a plurality of times in response to the transition of the reset signal, and the second control circuit is configured to perform the refresh operation on the memory cell array in response to each issuance of the refresh signal.