1. A device for receiving an external clock signal and operable in a normal mode of operation and an alternative mode of operation, comprising:
a control circuit for receiving a plurality input signals external to the device, wherein the control circuit assesses the input signals to determine whether the device is to enter a normal or alternative mode of operation;
clock generating circuitry for receiving the external clock signal, wherein the clock generating circuitry generates at least one internal clock signal during the normal mode and does not generate the at least one internal clock signal during the alternative mode; and
at least one subcircuit, wherein the subcircuit receives one of the internal clock signals during the normal mode, and wherein the subcircuit receives the external clock signal during the alternative mode.
2. The device of claim 1, wherein the input signals are not concurrently active to enter the normal mode, but wherein the input signals are concurrently active to enter the alternative mode.
3. The device of claim 1, wherein the input signals are asynchronous with external clock signal.
4. The device of claim 1, wherein at least one subcircuit comprises an input buffer.
5. The device of claim 1, wherein the clock generating circuitry comprises a delay locked loop.
6. The device of claim 1, wherein the device is a synchronous dynamic random access memory.
7. The device of claim 1, wherein one of the input signals comprises a reset signal.
8. The device of claim 1, wherein one of the input signals comprises a chip select signal.
9. The device of claim 1, wherein the input signals comprise reset and chip select signals.
10. The device of claim 1, wherein the alternative mode of operation is a test mode.
11. The device of claim 1, wherein the frequency of the external clock signal is lower for the alternative mode of operation than for the normal mode of operation.
12. The device of claim 1, wherein the input signals sequentially comprise:
activation of a second of the input signals;
activation of a first of the input signals;
deactivation of the first input signal; and
deactivation of the second input signal.
13. A device for receiving an external clock signal and operable in a normal mode of operation and an alternative mode of operation, comprising:
control circuitry for assessing a plurality of input signals external to the device and for determining whether the device is to enter a normal or alternative mode of operation; and
at least one subcircuit, wherein the subcircuit receives an internally-generated clock signal generated from the external clock signal during the normal mode, and wherein the subcircuit receives the external clock signal during the alternative mode.
14. The device of claim 13, wherein the input signals are not concurrently active to enter the normal mode, but wherein the input signals are concurrently active to enter the alternative mode.
15. The device of claim 13, wherein the input signals are asynchronous with the external clock signal.
16. The device of claim 13, wherein at least one subcircuit comprises an input buffer.
17. The device of claim 13, wherein the internally-generated clock signal is generated by a delay locked loop.
18. The device of claim 13, wherein the device is a synchronous dynamic random access memory.
19. The device of claim 13, wherein one of the input signals comprises a reset signal.
20. The device of claim 13, wherein one of the input signals comprises a chip select signal.
21. The device of claim 13, wherein the input signals comprise reset and chip select signals.
22. The device of claim 13, wherein the alternative mode comprises a test mode.
23. The device of claim 13, wherein the input signals sequentially comprise:
activation of a second of the input signals;
activation of a first of the input signals;
deactivation of the first input signal; and
deactivation of the second input signal.
24. A method of operating a device in a test mode, comprising:
applying an input signal to each of a plurality of terminals external to the device to place the device into a test mode;
in response to placing the device into the test mode, disabling the generation of the at least one internal clock signal; and
while in the test mode, applying an external clock signal to at least one subcircuits via an external clock input terminal.
25. The device of claim 24, wherein the input signals are not concurrently active to enter a normal mode, but wherein the input signals are concurrently active to enter the test mode.
26. The method of claim 24, wherein applying the external clock signal while in the test mode comprises use of an external clock signal of a frequency lower than that used during the normal mode.
27. The method of claim 24, wherein a first input signal is applied before a second input signal, but wherein the first input signal is unapplied after the second input signal is unapplied.
28. The method of claim 24, wherein the input signals are asynchronous with the external clock signal.
29. The method of claim 24, wherein the at least one internal clock signal is generated by a delay locked loop.
30. The method of claim 24, wherein the delay locked loop receives the external clock signal as an input.
31. The method of claim 24, wherein the device is a synchronous dynamic random access memory.
32. The method of claim 24, wherein one of the input signals comprises a reset signal.
33. The method of claim 24, wherein one of the input signals comprises a chip select signal.
34. The method of claim 24, wherein the input signals comprise a reset signal and a chip select signal.
35. The method of claim 24, wherein the input signals are applied in a predetermined relationship to place the device into the test mode, and wherein the predetermined relationship is not encountered during a normal mode.
36. A method of operating a device in a normal mode of operation and an alternative mode of operation, comprising in no particular order:
applying an input signal to each of a plurality of external terminals in a first predetermined sequence to place the device into a normal mode;
in response to placing the device into the normal mode, applying an internally-generated clock signal to at least one subcircuit;
applying an input signal to each of the plurality of external terminals in a second predetermined sequence to place the device into an alternative mode; and
in response to placing the device into the alternative mode, applying an external clock signal to the at least one subcircuit.
37. The method of claim 36, wherein applying the external clock signal in the alternative mode comprises use of an external clock signal of a frequency lower than that used during the normal mode.
38. The method of claim 36, wherein the second predetermined sequence comprises input signals concurrently applied to the plurality of input terminals.
39. The method of claim 38, wherein the second predetermined sequence comprises applying one of the input signals before, during, and after another input signal.
40. The method of claim 36, wherein the second predetermined sequence is not applied during the normal mode.
41. The method of claim 36, wherein the second predetermined sequence is asynchronous with the external clock signal.
42. The method of claim 36, wherein the internally-generated clock signal is generated using a delay locked loop.
43. The method of claim 36, wherein the device is a synchronous dynamic random access memory.
44. The method of claim 36, wherein one of the input signals comprises a reset signal.
45. The method of claim 36, wherein one of the input signals comprises a chip select signal.
46. The method of claim 36, wherein the input signals comprise a reset signal and a chip select signal.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A communication apparatus capable of radio communication with an active tag apparatus capable of data transmission and reception by radio, comprising:
a radio communication unit that conducts radio communication with the active tag apparatus;
a data storage unit that stores a frequency designation data including a local transmission frequency used for data transmission by the radio communication unit and specifying data on a frequency of a carrier sense to be carried out by the active tag apparatus; and
a control unit that causes the radio communication unit to transmit the frequency designation data stored in the data storage unit to the active tag apparatus at the local transmission frequency.
2. The communication apparatus according to claim 1,
wherein the control unit causes the radio communication unit to carry out the carrier sense at a plurality of given frequencies, and stores the detected carrier frequency data in the data storage unit.
3. An active tag apparatus capable of radio communication with a communication apparatus, comprising:
a radio communication unit capable of carrying out carrier sense at a plurality of frequencies and adapted to transmit and receive data at a specified radio frequency to and from the communication apparatus; and
a control unit which, upon detection that the data received from the communication apparatus by the radio communication unit contains a frequency designation data specifying a frequency for the carrier sense to be carried out, designates to the radio communication unit, based on the received frequency designation data, the frequency for the carrier sense to be carried out.
4. A system comprising an active tag apparatus capable of data transmission and reception by radio and a communication apparatus for conducting radio communication with the active tag apparatus;
wherein the communication apparatus includes:
a radio communication unit that conducts the radio communication with the active tag apparatus;
a data storage unit that stores a frequency designation data including a local transmission frequency used by the radio communication unit at a time of data transmission and specifying data on a frequency for carrier sense to be carried out by the active tag apparatus; and
a control unit for causing the radio communication unit to transmit the frequency designation data stored in the data storage unit to the active tag apparatus at the local transmission frequency; and
wherein the active tag apparatus includes:
a radio communication unit capable of carrying out the carrier sense at a plurality of frequencies and conducting data transmission and reception at a specified frequency by radio with the communication apparatus; and
a control unit which, upon detection that the data received from the communication apparatus by the radio communication unit contains a frequency designation data specifying data on a frequency for the carrier sense to be carried out, designates to the radio communication unit the frequency for the carrier sense to be carried out, based on the received frequency designation data.
5. An active tag apparatus capable of radio communication with a communication apparatus, comprising:
a radio communication unit capable of carrying out carrier sense at a plurality of frequencies and measuring a reception strength of a received radio wave to transmit and receive data at a specified radio frequency to and from the communication apparatus;
a data storage unit that stores, in correspondence with each other, a maximum reception strength frequency and a designated frequency specifying a frequency for the carrier sense to be carried out; and
a control unit that
causes the radio communication unit to carry out the carrier sense at the plurality of frequencies,
receives a result of measuring the reception strength for each of the plurality of frequencies,
specifies a particular frequency from among the plurality of frequencies as the maximum reception strength frequency from the measurement result,
reads the designated frequency corresponding to the particular frequency from the data storage unit and
causes the radio communication unit to carry out the carrier sense at the designated frequency.
6. A computer program product stored on a tangible computer-readable medium for a communication apparatus capable of conducting radio communication with an active tag apparatus capable of data transmission and reception by radio, the computer program product comprising computer executable instructions that causes a computer of the communication apparatus to execute:
reading frequency designation data from a data storage unit storing a frequency designation data including a local transmission frequency used for data transmission by radio communication and specifying data on a frequency for carrier sense to be carried out by the active tag apparatus; and
causing transmission by radio communication of the read frequency designation data at the local transmission frequency to the active tag apparatus.
7. A computer program product stored on a tangible computer-readable medium for an active tag apparatus having a radio communication unit adapted to carry out carrier sense at a plurality of frequencies and transmit and receive data to and from a-communication apparatus at a specified radio frequency, the computer program product comprising computer executable instructions that causes a computer functioning as the active tag apparatus to execute:
judging whether the data received by the radio communication unit from the data read-write apparatus contains frequency designation data specifying data on a frequency for the carrier sense to be carried out; and
upon judgment that the frequency designation data is so contained, designating to the radio communication unit a frequency for the carrier sense to be carried out, based on the received frequency designation data.
8. A computer program product stored on a tangible-readable medium for an active tag apparatus including a radio communication unit adapted to carry out carrier sense at a plurality of frequencies while at a same time measuring a reception strength of received radio wave to transmit and receive data to and from a communication apparatus at a specified radio frequency, and a reception strength measurement unit for measuring the reception strength of the received radio wave from output of the radio communication unit, the computer program product comprising computer executable instructions that cause a computer functioning as the active tag apparatus to execute:
causing the radio communication unit to carry out the carrier sense at the plurality of frequencies;
receiving a measurement result of the reception strength for each of the plurality of frequencies;
specifying a particular frequency from among the plurality of frequencies as a maximum reception strength frequency from the measurement result;
reading the designated frequency corresponding to the particular frequency from a data storage unit storing, in correspondence with each other, the maximum reception strength frequency and the designated frequency specifying a frequency for the carrier sense to be carried out; and
causing the radio communication unit to carry out the carrier sense at the designated frequency.
9. A system, comprising:
a plurality of communication apparatuses for conducting radio communication at a plurality of frequencies; and
an active tag apparatus capable of data transmission and reception by radio with the communication apparatus only by executing carrier sense at selected frequencies from among the plurality of frequencies of communication apparatuses within transceiving range of the active tag apparatus.
10. The system according to claim 9, wherein one or more of the communication apparatuses each comprise:
a data storage unit that stores frequency designation data including a local transmission frequency used for data transmission by the radio communication and data on a frequency of a carrier sense to be carried out by the active tag apparatus; and
a controller that transmits the frequency designation data stored in the data storage unit to the active tag apparatus at the local transmission frequency for causing the active tag apparatus to select a frequency for executing a carrier sense according to the frequency designation data when the communication apparatus enters the active tag apparatus transceiving range.
11. The system according to claim 9, wherein the active tag apparatus comprises:
a data storage unit that stores, in correspondence with each other, a maximum reception strength frequency and a selected frequency specifying a frequency for the carrier sense to be executed; and
a controller
executing carrier sense at a plurality of frequencies;
measuring a reception strength of a received radio wave to transmit and receive data at a specified radio frequency to and from the communication apparatuses;
receiving a result of measuring the reception strength for each of the plurality of frequencies,
determining a particular frequency from among the plurality of frequencies as the maximum reception strength frequency according to the measurement result,
selecting a frequency corresponding to the particular frequency as the maximum reception strength frequency from the data storage unit, and
executing the carrier sense at the selected frequency.
12. The system according to claim 10, wherein the controller executes carrier sense at the plurality of frequencies according to frequencies use by other communication apparatuses, and stores the detected carrier frequency data in the data storage unit.