概觀
ISSI’s 256-Mbit DDR SDRAM achieves high speed data
transfer using pipeline architecture and two data word
accesses per clock cycle. The 268,435,456-bit memory
array is internally organized as four banks of 64Mb to
allow concurrent operations. The pipeline allows Read
and Write burst accesses to be virtually continuous, with
the option to concatenate or truncate the bursts. The
programmable features of burst length, burst sequence
and CAS latency enable further advantages. The device
is available in 8-bit, 16-bit and 32-bit data word size
Input data is registered on the I/O pins on both edges
of Data Strobe signal(s), while output data is referenced
to both edges of Data Strobe and both edges of CLK.
Commands are registered on the positive edges of CLK.
An Auto Refresh mode is provided, along with a Self
Refresh mode. All I/Os are SSTL_2 compatible.