Semiconductor memory device and control method thereof
View Patent ↗A semiconductor memory device includes: a command latch circuit that latches a command signal; an address latch circuit that latches an address signal; a mode latch circuit that latches a mode signal; and a command decoder that selects the address latch circuit in response to the latch of a normal command by the command latch circuit, and selects the mode latch circuit in response to the latch of an adjustment command. With this arrangement, the mode signal can be dynamically received without performing a mode register set. Therefore, when a sufficiently large latch margin of the mode latch circuit is secured, there is no risk that it becomes impossible to input the mode signal.
1. A semiconductor device, comprising:
terminals supplied selectively with an address signal or a mode signal;
an address latch circuit coupled, when selected, to the terminals to latch the address signal; and
a mode latch circuit coupled, when selected, to the terminals to latch the mode signal,
wherein the terminals are supplied with the address signal when the semiconductor device is in a first mode, the terminals being supplied with the mode signal when the semiconductor device is in a second mode, the address latch circuit latching the address signal in the first mode, and the mode latch circuit latching the mode signal in the second mode, and
wherein the address signal is latched in synchronization with an internal clock signal in the first mode, the internal clock signal being generated by causing a first delay in an external clock signal, and an amount of the first delay being controlled by the mode signal.
2. The semiconductor device as claimed in claim 1 , further comprising command terminals, wherein the first mode is functioned when the command terminals are supplied with a first command signal and the second mode is functioned when the command terminals are supplied with a second command signal.
3. The semiconductor device as claimed in claim 1 , wherein the mode latch circuit latches the mode signal in synchronization with an additional internal clock signal and the additional internal clock is generated by causing a second delay in the external clock signal and an amount of the second delay is fixed.
4. The semiconductor device as claimed in claim 1 , wherein the address signal comprises a first address signal and a second address signal supplied after the first address signal, and the address latch circuit including a first address latch circuit which latches the first address signal in synchronization with a rising edge of the internal clock signal and a second address latch circuit which latches the second address signal in synchronization with a trailing edge of the internal clock signal.
5. The semiconductor device as claimed in claim 3 , wherein the additional internal clock is substantially the same in frequency as the internal clock and different in phase from the internal clock.