Sep.'99 Preliminary

MITSUBISHI LSIs

MITSUBISHI

ELECTRIC

DDR SDRAM (Rev.0.0)

M2S56D20/ 30 TP

256M Double Data Rate Synchronous DRAM

5

BASIC FUNCTIONS

The M2S56D20/30TP provides basic functions, bank (row) activate, burst read / write, bank (row)

precharge, and auto / self refresh. Each command is defined by control signals of /RAS, /CAS and /WE at

CLK rising edge. In addition to 3 signals, /CS ,CKE and A10 are used as chip select, refresh option, and

precharge option, respectively. To know the detailed definition of commands, please see the command

truth table.

/CS

Chip Select : L=select, H=deselect

/RAS

Command

/CAS

Command

/WE

Command

CKE

Refresh Option @refresh command

A10

Precharge Option @precharge or read/write command

CLK

define basic commands

Activate (ACT) [/RAS =L, /CAS =/WE =H]

ACT command activates a row in an idle bank indicated by BA.

Read (READ) [/RAS =H, /CAS =L, /WE =H]

READ command starts burst read from the active bank indicated by BA. First output data appears after

/CAS latency. When A10 =H at this command, the bank is deactivated after the burst read (auto-

precharge,READA)

Write (WRITE) [/RAS =H, /CAS =/WE =L]

WRITE command starts burst write to the active bank indicated by BA. Total data length to be written

is set by burst length. When A10 =H at this command, the bank is deactivated after the burst write (auto-

precharge, WRITEA).

Precharge (PRE) [/RAS =L, /CAS =H, /WE =L]

PRE command deactivates the active bank indicated by BA. This command also terminates burst read

/write operation. When A10 =H at this command, all banks are deactivated (precharge all, PREA).

Auto-Refresh (REFA) [/RAS =/CAS =L, /WE =CKE =H]

REFA command starts auto-refresh cycle. Refresh address including bank address are generated

internally. After this command, the banks are precharged automatically.

/CLK