Semiconductor device including latency counter

1. A semiconductor device comprising:

a command input line;

a command output line; and

first and second latency counters connected in series between the command input line and the command output line, wherein

one of the first and second latency counters supplies an internal command signal to the command output line when a predetermined latency elapses after the internal command signal is supplied to the other of the first and second latency counters from the command input line,

the first latency counter selects whether to give the internal command signal an odd-cycle latency based on first control information, and

the second latency counter gives the internal command signal a latency at intervals of two cycles based on second control information.

2. The semiconductor device as claimed in claim 1 , wherein the predetermined latency is an integral multiple of a clock cycle of an external clock signal supplied from outside.

3. The semiconductor device as claimed in claim 2 , wherein the first latency counter includes:

a first register that latches the internal command signal in synchronization with an internal clock signal that has the same clock cycle as the external clock signal; and

a first selector that selects one of the internal command signal that has passed through the first register and the internal command signal that has not passed through the first register.

4. The semiconductor device as claimed in claim 3 , wherein

the second latency counter includes a plurality of synchronous circuits,

each of the synchronous circuits includes second and third registers connected in series, and

each of the second and third registers latches the internal command signal in synchronization with the internal clock signal.

5. The semiconductor device as claimed in claim 4 , wherein

the second latency counter further includes a plurality of second selectors each provided to an associated one of the synchronous circuits,

each of the second selectors select one of the internal command signal that passes through the second and third registers and the internal command signal that does not pass through the second and third registers based on an associated bit of the second control information.

6. The semiconductor device as claimed in claim 5 , wherein

each one of the synchronous circuits and corresponding one of the second selectors constitute a set, the sets being connected in series, and

the internal command signal supplied to the second latency counter is supplied to any one of the synchronous circuits selected by the second selectors based on the second control information.

7. The semiconductor device as claimed in claim 2 , further comprising a frequency dividing circuit that generates first and second internal clock signals each having double the clock cycle of the external clock signal, the first and second internal clock signals having different phase from each other by an amount equivalent to the clock cycle of the external clock signal,

wherein the first latency counter includes:

a first selector that outputs, based on the first control information, the internal command signal that is captured from the command input line in synchronization with one of the first and second internal clock signals; and

a second selector that outputs, based on the first control information, the internal command signal that is captured from the command input line in synchronization with the other of the first and second internal clock signals.

8. The semiconductor device as claimed in claim 7 , wherein

the first latency counter further includes:

a first register that latches the internal command signal on the command input line in synchronization with the first internal clock signal;

a second register that latches the internal command signal on the command input line in synchronization with the second internal clock signal;

a third register that latches the internal command signal output from the second register in synchronization with the first internal clock signal; and

a fourth register that latches the internal command signal output from the first register in synchronization with the second internal clock signal,

the first selector selects one of the internal command signals output from the first and third registers based on the first control information, and

the second selector selects one of the internal command signals output from the second and fourth registers based on the first control information.

9. The semiconductor device as claimed in claim 8 , wherein

the first register performs a latch operation in synchronization with one of active edges of the first internal clock signal,

the second register performs a latch operation in synchronization with one of active edges of the second internal clock signal,

the third register performs a latch operation in synchronization with the other of active edges of the first internal clock signal, and

the fourth register performs a latch operation in synchronization with the other of active edges of the second internal clock signal.

10. The semiconductor device as claimed in claim 9 , wherein

the third register passes through the internal command signal supplied from an input node thereof to an output node thereof without performing the latch operation during a period between the one of active edges and the other of active edges of the first internal clock signal, and

the fourth register passes through the internal command signal supplied from an input node thereof to an output node thereof without performing the latch operation during a period between the one of active edges and the other of active edges of the second internal clock signal.

11. The semiconductor device as claimed in claim 7 , wherein

the second latency counter includes a plurality of first synchronous circuits, a plurality of second synchronous circuits, a plurality of third selectors and a plurality of fourth selectors,

each one of the first synchronous circuits and corresponding one of the third selectors constitute a first set, the first sets being connected in series,

each one of the second synchronous circuits and corresponding one of the fourth selectors constitute a second set, the second sets being connected in series,

each of the first synchronous circuits latches the internal command signal supplied thereto in synchronization with the first internal clock signal,

each of the second synchronous circuits latches the internal command signal supplied thereto in synchronization with the second internal clock signal,

each of the third selectors selects one of the internal command signal that passes through a corresponding first synchronous circuit and the internal command signal that does not pass through a corresponding first synchronous circuit based on an associated bit of the second control information, and

each of the fourth selectors selects one of the internal command signal that passes through a corresponding second synchronous circuit and the internal command signal that does not pass through a corresponding second synchronous circuit based on an associated bit of the second control information.

12. The semiconductor device as claimed in claim 11 , wherein

the internal command signal supplied from the first selector is supplied to any one of the first synchronous circuits selected by the third selectors based on the second control information, and

the internal command signal supplied from the second selector is supplied to any one of the second synchronous circuits selected by the fourth selectors based on the second control information.

13. The semiconductor device as claimed in claim 1 , further comprising a command decoder that generates the internal command signal based on an external command signal issued from outside, and supplies the command input line with the internal command signal.

14. The semiconductor device as claimed in claim 13 , further comprising:

a memory cell array that includes a plurality of memory cells;

a row system control circuit that controls a timing of row access to the memory cell array; and

a column system control circuit that controls a timing of column access to the memory cell array,

wherein the column system control circuit operates in response to the internal command signal on the command output line.

15. The semiconductor device as claimed in claim 5 , wherein

each bit of the second control information is supplied to an associated one of the synchronous circuits, and

each of the synchronous circuits invalidates an operation thereof in synchronization with the internal clock signal based on a logic level of the associated bit of the second control information.

16. The semiconductor device as claimed in claim 11 , wherein

each bit of the second control information is supplied to an associated one of the first synchronous circuits and an associated one of the second synchronous circuits,

each of the first synchronous circuits invalidates an operation thereof in synchronization with the first internal clock signal based on a logic level of the associated bit of the second control information, and

each of the second synchronous circuits invalidates an operation thereof in synchronization with the second internal clock signal based on a logic level of the associated bit of the second control information.

17. A semiconductor device comprising:

a command input line;

a command output line; and

first and second latency counters connected in series between the command input and output lines, each of the first and second latency counters being supplied with a clock signal, the first latency counter being configured to represent a selected one of an odd-cycle latency and a zero-cycle latency of the clock signal in response to first control information, and the second latency counter being configured to represent a selected one of an even-cycle latency and a zero-cycle latency of the clock signal in response to second control information.

18. The device as claimed in claim 17 , wherein the first latency counter is connected to the command input line and the second latency counter is connected between the first latency counter and the command output line.

19. The device as claimed in claim 17 , wherein the second latency counter includes a plurality of unit circuits connected in series, each of the unit circuits giving a selected one of a two-cycle latency and a zero-cycle latency of the clock signal.

20. The device as claimed in claim 19 , wherein the second control information includes a plurality of control signals each coupled to an associated one of the unit circuits, each of the unit circuits giving the two-cycle latency of the clock signal when an associated one of the control signals takes a first state and the zero-cycle latency of the clock signal when the associated one of the control signals takes a second state.

21. The device as claimed in claim 20 , wherein the first latency counter represents a selected one of a one-cycle latency and a zero-cycle latency of the clock signal.

22. The device as claimed in claim 20 , wherein the first latency counter represents a selected one of a three-cycle latency and a zero-cycle latency of the clock signal.

23. A semiconductor device comprising:

a command input line;

a command output line; and

first and second latency counters connected in series between the command input and output lines, each of the first and second latency counters being supplied with a clock signal, the first latency counter being configured to represent a selected one of an even-cycle latency and an odd-cycle latency of the clock signal in response to first control information, and the second latency counter being configured to represent a selected one of an even-cycle latency and a zero-cycle latency of the clock signal in response to second control information.

24. The device as claimed in claim 23 , wherein the first latency counter includes first and second register circuits coupled in series and a first selector including a first input node receiving an output of the first register circuit and a second input node receiving an output of the second register circuit.

25. The device as claimed in claim 24 , wherein the first selector selects the first input node when the first control information takes a first state and the second input node when the first control information takes a second state.

26. The device as claimed in claim 25 , wherein the first latency counter further includes one or more additional register circuits coupled in series to the first register circuit.

27. The device as claimed in claim 23 , wherein the first latency counter is coupled between the command input line and the second latency counter, and the second latency counter is coupled between the first latency counter and the command output line.

28. The device as claimed in claim 23 , wherein the second latency counter is coupled between the command input line and the first latency counter, and the first latency counter is coupled between the second latency counter and the command output line.

29. The device as claimed in claim 24 , wherein the first latency counter is coupled between the command input line and an intermediate node, and the second latency counter is coupled between the intermediate node and the command output

30. The device as claimed in claim 29 , wherein the second latency counter includes a plurality of unit circuits connected in series, each of the unit circuits representing a selected one of an even-cycle latency and a zero-cycle latency of the clock signal.

31. The device as claimed in claim 30 , wherein the second control information includes a plurality of control signals each coupled to an associated one of the unit circuits, each of the unit circuits representing an even-cycle latency of the clock signal when an associated one of the control signals takes a first state and a zero-cycle latency of the clock signal when the associated one of the control signals takes a second state.

32. The device as claimed in claim 30 , wherein each of the unit circuits comprises a second selector including a first input terminal, a second input terminal, and an output terminal, a circuit node, and an even number of registers coupled in series between the first input terminal and the circuit node, each of the unit circuits being coupled such that the output terminal of a preceding one of the unit circuits is coupled to the circuit node of a succeeding one of the unit circuits and that the circuit node of a leading one of the unit circuits and the second terminal of each of the unit circuits are coupled to the intermediate node.

33. The device as claimed in claim 24 , wherein the second latency counter is coupled between the command input line and an intermediate node, and the first latency counter is coupled between the intermediate node and the command output line.

34. The device as claimed in claim 33 , wherein the second latency counter includes a plurality of unit circuits connected in series, each of the unit circuits representing a selected one of an even-cycle latency and a zero-cycle latency of the clock signal.

35. The device as claimed in claim 34 , wherein the second control information includes a plurality of control signals each coupled to an associated one of the unit circuits, each of the unit circuits representing an even-cycle latency of the clock signal when an associated one of the control signals takes a first state and a zero-cycle latency of the clock signal when the associated one of the control signals takes a second state.

36. The device as claimed in claim 34 , wherein each of the unit circuits comprises a second selector including a first input terminal, a second input terminal, and an output terminal, a circuit node, and an even number of registers coupled in series between the first input terminal and the circuit node, each of the unit circuits being coupled such that the output terminal of a preceding one of the unit circuits is coupled to the circuit node of a succeeding one of the unit circuits and that the circuit node of a leading one of the unit circuits and the second terminal of each of the unit circuits are coupled to the command input line.

37. The device as claimed in claim 23 , further comprising:

a memory cell array that includes a plurality of memory cells;

a control circuit that reads out data from a selected one of the memory cells; and

an output circuit that responds to a signal of the command output line to output a data signal indicative of the data.

38. The device as claimed in claim 23 , wherein the even-cycle latency represented by the first latency counter excludes a zero-cycle latency.