Semiconductor device having PDA function

1. A semiconductor device comprising:

a command decoder activating a first mode register setting signal in response to a mode register setting command issued from outside;

a first latency shifter activating a second mode register setting signal after elapse of predetermined cycles of a clock signal since the first mode register setting signal is activated; and

a mode register storing a mode signal supplied from outside in response to the second mode register setting signal.

2. The semiconductor device as claimed in claim 1 , further comprising a plurality of address terminals supplied with the mode signal.

3. The semiconductor device as claimed in claim 1 , further comprising a plurality of command terminals supplied with a command signal constituted of a plurality of bit signals, the mode register setting command being indicated by a predetermined logical combination of the bit signals.

4. The semiconductor device as claimed in claim 1 , further comprising a clock terminal supplied with the clock signal from outside.

5. The semiconductor device as claimed in claim 1 , further comprising a data terminal supplied with a data signal from outside,

wherein the mode register stores the mode signal in response to the second mode register setting signal and the data signal.

6. The semiconductor device as claimed in claim 1 , further comprising:

a first circuit supplying the first mode register setting signal to the first latency shifter in a first operation mode, and supplying the first mode register setting signal to the mode register without supplying to the first latency shifter in a second operation mode; and

a second circuit that supplies the second mode register setting signal to the mode register in the first operation mode, and supplies the first mode register setting signal to the mode register in the second operation mode.

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

the first circuit is coupled between the command decoder and the first latency shifter, and

the second circuit is coupled between the first latency shifter and the mode register.

8. The semiconductor device as claimed in claim 6 , further comprising a data terminal supplied with a data signal from outside,

wherein the mode register stores the mode signal in response to the second mode register setting signal and the data signal in the first operation mode, and stores the mode signal in response to the first mode register setting signal in the second operation mode.

9. The semiconductor device as claimed in claim 8 , further comprising a third circuit coupled between the first latency shifter and the mode register, the third circuit controlling whether to supply the second mode register setting signal to the mode register based on the data signal.

10. The semiconductor device as claimed in claim 1 , further comprising a delay circuit delaying the second mode register setting signal in synchronism with the clock signal.

11. The semiconductor device as claimed in claim 1 , wherein

the command decoder further activates a first write signal in response to a write command issued from outside, and

the semiconductor device further comprises a second latency shifter activating a second write signal after elapse of the predetermined cycles of the clock signal since the first write signal is activated.

12. The semiconductor device as claimed in claim 11 , further comprising a data input/output circuit capturing a data signal supplied from outside in association with the second write signal.

13. The semiconductor device as claimed in claim 1 , wherein

the command decoder further activates a first write signal in response to a write command supplied from outside,

the semiconductor device further comprises a fourth circuit coupled between the command decoder and the first latency shifter, the fourth circuit supplying one of the first write signal and the first mode register setting signal to the first latency shifter, and

the first latency shifter activates the second mode register setting signal after elapse of the predetermined cycles of the clock signal since the first write signal is activated.

14. The semiconductor device as claimed in claim 13 , further comprising a fifth circuit coupled between the first latency shifter and the mode register, the fifth circuit controlling whether to supply the second mode register setting signal to the mode register.

15. The semiconductor device as claimed in claim 13 , further comprising a FIFO circuit that stores the mode signal in response to the first mode register setting signal and outputs the mode signal stored therein in response to the second mode register setting signal.

16. The semiconductor device as claimed in claim 15 , further comprising:

a sixth circuit supplying one of an address signal and the mode signal to the FIFO circuit, the address signal being supplied from outside in association with the first write signal; and

a seventh circuit supplying one of the mode signal passed through the FIFO circuit and the mode signal not passed through the FIFO circuit to the mode register.

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

the sixth circuit supplies the mode signal to the FIFO circuit in a first operation mode, and supplies the address signal to the FIFO circuit in a second operation mode, and

the seventh circuit supplies the mode signal passed through the FIFO circuit to the mode register in the first operation mode, and supplies the mode signal not passed through the FIFO circuit to the mode register in the second operation mode.

18. The semiconductor device according to claim 16 , further comprising:

a plurality of address terminals supplied with the mode signal and the address signal from outside; and

an address latch circuit that latches the mode signal and the address signal supplied through the address terminals,

wherein the sixth circuit is coupled between the address latch circuit and the FIFO circuit, and the seventh circuit is coupled between the FIFO circuit and the mode register.

19. The semiconductor device as claimed in claim 1 , wherein the predetermined cycle coincides with a write latency that indicates a period between when a write command is issued to the semiconductor device and when a data signal is supplied to a data terminal from outside.

20. A semiconductor device comprising:

a first external terminal receiving a command signal;

a second external terminal receiving a data signal;

a third external terminal receiving an address signal;

a command decoder configured to output a mode register setting signal based on the command signal;

a latency shifter configured to receive the mode register setting signal and output a shifted mode register setting signal;

a logic gate configured to receive the shifted mode register setting signal and a portion of the data signal and output a second mode register setting signal; and

a mode register configured to receive the second mode register setting signal and a portion of the address signal.