Semiconductor memory device having clock generation scheme based on command
A semiconductor memory device includes a command decoder configured to generate an auto-sync signal in response to a command for writing data at a memory cell or reading data from a memory cell, and an internal data clock generating circuit configured to phase synchronize a second clock, having a clock frequency higher than a clock frequency of a first clock, with the first clock in response to the auto-sync signal.
1. A memory device comprising:
a command decoder configured to decode a column address strobe (CAS) command synchronized with a first clock;
an internal data clock generating circuit configured to perform a synchronization between the first clock and a second clock in response to the CAS command; and
a pattern generator configured to generate an error data code (EDC) hold pattern in response to the CAS command.
2. The memory device of claim 1 , further comprising:
an input/output control circuit configured to control data input/output based on the second clock synchronized with the first clock.
3. The memory device of claim 2 , wherein the internal data clock generating circuit performs the synchronization between the first clock and the second clock during a latency of the data input/output.
4. The memory device of claim 2 , wherein the internal data clock generating circuit includes:
a data clock divider configured to divide the second clock into multi-phase clocks; and
a phase switch configured to perform swapping of the multi-phase clocks.
5. The memory device of claim 1 , wherein the second clock is toggled after the CAS command is received by the command decoder.
6. The memory device of claim 2 , wherein the pattern generator is further configured to output the EDC hold pattern before read data are output by the input/output control circuit.
7. The memory device of claim 6 , wherein the pattern generator is further configured to end outputting the EDC hold pattern, when outputting the read data is completed by the input/output control circuit.
8. The memory device of claim 1 , wherein the EDC hold pattern is generated for each rank in a case of a multi-rank structure.
9. A memory device comprising:
a decoder configured to receive a command for selecting one of a first mode and a second mode;
a dual clock managing circuit configured to selectively activate one of a first mode clock generator and a second mode clock generator based on a selected mode; and
an input/output control circuit configured to control a first data input/output at a first frequency in the first mode and control a second data input/output at a second frequency in the second mode, the second frequency being lower than the first frequency;
wherein the first mode clock generator uses a first system clock having a first clock frequency and a data clock having a clock frequency higher than the first clock frequency, and
wherein the second mode clock generator uses a second system clock having a second clock frequency and a data strobe signal of which a frequency is the same as the second clock frequency.
10. The memory device of claim 9 , wherein the decoder is further configured to generate a mode register set (MRS) signal in response to the command.
11. The memory device of claim 9 , wherein the input/output control circuit is further configured to:
perform the first data input/output based on the data clock in the first mode, and
perform the second data input/output based on the data strobe signal in the second mode.
12. The memory device of claim 9 , further comprising an internal data clock generating circuit configured to perform a synchronization between the first system clock and the data clock in response a column address strobe (CAS) command,
wherein the decoder is further configured to decode the CAS command synchronized with the first system clock.
13. The memory device of claim 12 , further comprising a pattern generator configured to generate an error data code (EDC) hold pattern in response to the CAS command.
14. The memory device of claim 12 , wherein the internal data clock generating circuit performs the synchronization between the first system clock and the data clock during a latency of the first data input/output.
15. The memory device of claim 12 , wherein the data clock is toggled after the CAS command is received by the decoder.
16. A memory system comprising:
a memory controller generating a first clock, a second clock, and a column address strobe (CAS) command; and
a memory device including:
a command decoder configured to decode the CAS command synchronized with the first clock;
an internal data clock generating circuit configured to perform a synchronization between the first clock and the second clock in response to the CAS command; and
a pattern generator configured to generate an error data code (EDC) hold pattern in response to the CAS command.
17. The memory system of claim 16 , wherein the memory controller includes a clock data recovery (CDR) circuit configured to receive the EDC hold pattern.
18. The memory system of claim 16 , wherein the memory controller toggles the second clock after providing the CAS command to the memory device.
19. The memory system of claim 16 , wherein the memory controller includes:
a first clock circuit configured to generate the first clock and the second clock; and
a second clock circuit configured to generate a third clock and a data strobe signal, and
wherein a frequency of the second clock is higher than a frequency of the first clock, and
wherein a frequency of the data strobe signal is the same as a frequency of the third clock.
20. The memory system of claim 19 , wherein the command decoder is further configured to decode a command for selecting one of a first mode and a second mode, and
the memory device further includes:
a dual clock managing circuit configured to selectively activate one of a first mode clock generator and a second mode clock generator based on a selected mode; and
an input/output control circuit configured to control a first data input/output at a first frequency in the first mode and control a second data input/output at a second frequency in the second mode, the second frequency being lower than the first frequency.
21. A memory device comprising:
a command decoder configured to generate an auto-sync signal in response to a column address strobe (CAS) command; and
an internal data clock generating circuit configured to adjust a phase of a second clock to be synchronized with a phase of a first clock in response to the auto-sync signal, wherein a frequency of the second clock is higher than a frequency of the first clock,
wherein the auto-sync signal is a pulse signal which is delayed by a first predetermined time or a second predetermined time with respect to the CAS command, and
wherein the second clock starts to toggle after the CAS command is received.
22. The memory device of claim 21 , wherein the first predetermined time is the same as or different from the second predetermined time.