IS43DR81280C-25DBLI

ISSI's 1Gb DDR2 SDRAM uses a double-data-rate architecture to achieve high-speed operation. The double-data rate architecture is essentially a 4n-prefetch architecture, with an interface designed to transfer two data words per clock cycle at the I/O balls. Read and write accesses to the DDR2 SDRAM are burst oriented; accesses start at a selected location and continue for a burst length of four or eight in a programmed sequence. Accesses begin with the registration of an Active command, which is then followed by a Read or Write command. The address bits registered coincident with the active command are used to select the bank and row to be accessed (BA0-BA2 select the bank; A0-A12(x16) or A0-A13(x8) select the row). The address bits registered coincident with the Read or Write command are used to select the starting column location A0-A9 for the burst access and to determine if the auto precharge A10 command is to be issued. Prior to normal operation, the DDR2 SDRAM must be initialized. The following sections provide detailed information covering device initialization, register definition, command descriptions and device operation.

• Vdd = 1.8V ±0.1V, Vddq = 1.8V ±0.1V
• JEDEC standard 1.8V I/O (SSTL_18-compatible)
• Double data rate interface: two data transfers per clock cycle
• Differential data strobe (DQS, DQS)
• 4-bit prefetch architecture
• On chip DLL to align DQ and DQS transitions with CK
• 8 internal banks for concurrent operation
• Programmable CAS latency (CL) 3, 4, 5, 6 and 7 supported
• Posted CAS and programmable additive latency (AL) 0, 1, 2, 3, 4, 5 and 6 supported
• WRITE latency = READ latency - 1 tCK
• Programmable burst lengths: 4 or 8
• Adjustable data-output drive strength, full and reduced strength options
• On-die termination (ODT)