Semiconductor memory system including a plurality of semiconductor memory devices
A communication line is connected to first and second chips, and held at a first signal level. A monitor circuit changes a signal level of the communication line from the first signal to a second signal level while one of the first and second chips uses a current larger than a reference current. When the signal level of the communication line is the second signal level, the other of the first and second chips is controlled to a wait state that does not transfer to an operating state of using a current larger than the reference current.
1. A method for controlling a semiconductor memory system,
the system comprising:
a first semiconductor memory device; and
a signal line connected to the first semiconductor memory device,
wherein the first semiconductor memory device outputs a signal according to existence of a peak current to the signal line,
the method comprising:
causing, when the peak current is larger than a reference current, the first semiconductor memory device to be in a waiting state that does not transfer to an operating state using the current larger than the reference current.
2. The method according to claim 1 , wherein
the system further comprises a second memory device connected to the signal line.
3. The method according to claim 2 , wherein
the causing the first semiconductor memory device to be in the waiting state includes:
causing the first semiconductor memory device to output a signal to the signal line according to a first peak current of the first semiconductor memory device; and
causing the second semiconductor memory device to output a signal to the signal ine according to a second peak current of the second semiconductor memory device.
4. The method according to claim 3 , wherein
when the first semiconductor memory device receives a first signal from the signal line, the first semiconductor memory device goes into the waiting state that does not transfer to the operating state using the current larger than the reference current, the first signal indicating peak current which is larger than the reference current, and
when the second semiconductor memory device receives a second signal from the signal line, the second semiconductor memory device goes into the waiting state, the second signal indicating peak current which is larger than the reference current.
5. The method according to claim 4 , wherein
the signal line is a common communication line, the common communication line kept at the first level.
6. The method according to claim 5 , wherein
the system further includes:
a control circuit connected to the common communication signal line, and
the method further includes:
causing the control circuit to change a level of the common communication signal line from the first level to the second level while one of the first and second semiconductor memory devices uses a current larger than the reference current, and
causing the control circuit to control the other of the first and second semiconductor memory devices to the waiting state that does not transfer to an operating state using a current larger than the reference current during when the level of the common communication signal line is the second level.
7. The method according to claim 6 , wherein
the system further comprises a third memory device connected to the signal line.
8. The method according to claim 7 , wherein
each of the first to third semiconductor memory devices is a NAND flash memory.