GENERAL DESCRIPTION
The 128Mb DDR SDRAM uses a double-data-rate architecture to achieve high-speed operation. The double data rate architecture is essentially a 2n prefetch architecture with an interface designed to transfer two data words per clock cycle at the I/O pins. A single read or write access for the 128Mb DDR SDRAM effectively consists of a single 2n-bit wide, one clock cycle data transfer at the internal DRAM core and two corresponding n-bit wide, one-half-clock-cycle data transfers at the I/O pins. A bidirectional data strobe (DQS) is transmitted externally, along with data, for use in data capture at the receiver. DQS is a strobe transmitted by the DDR SDRAM during Reads and by the memory controller during Writes. DQS is edgealigned with data for Reads and center-aligned with data for Writes. The 128Mb DDR SDRAM operates from a differential clock (CK and CK ; the crossing of CK going high and CK going LOW is referred to as the positive edge of CK). Commands (address and control signals) are registered at every positive edge of CK.
AMIC Technology
