| 摘要 |
A Synchronous Dynamic Random Access Memory (SDRAM) has its operation mode selected to be the Single Data Rate (SDR) mode in response to the first state of the external terminal (OPT), thereby releasing data, which has been read out of a memory mat, in response to a clock signal produced by a clock regenerating circuit having a function of comparing the phases of the input and output of the circuit, or selected to be the Double Data Rate (DDR) mode in response to the second state of the external terminal (OPT), thereby releasing data, which has been read out of the memory mat, in response to a clock signal produced by a clock signal generation circuit in synchronism with an external clock. In the SDR mode, data are transferred via data lines in SDRAM unidirectionally and in the DDR mode, data are transferred via the data lines bidirectionally.
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