EDD5104ABTA, EDD5108ABTA
Read/Write Operations
Bank active
A read or a write operation begins with the bank active command [ACT]. The bank active command determines a
bank address and a row address. For the bank and the row, a read or a write command can be issued tRCD after
the ACT is issued.
Read operation
The burst length (BL), the /CAS latency (CL) and the burst type (BT) of the mode register are referred when a read
command is issued. The burst length (BL) determines the length of a sequential output data by the read command
that can be set to 2, 4, or 8. The starting address of the burst read is defined by the column address, the bank select
address which are loaded via the A0 to A12 and BA0, BA1 pins in the cycle when the read command is issued. The
data output timing are characterized by CL (2 or 2.5) and tAC. The read burst start CL • tCK + tAC (ns) after the
clock rising edge where the read command are latched. The DDR SDRAM output the data strobe through DQS
simultaneously with data. tRPRE prior to the first rising edge of the data strobe, the DQS are driven Low from VTT
level. This low period of DQS is referred as read preamble. The burst data are output coincidentally at both the
rising and falling edge of the data strobe. The DQ pins become High-Z in the next cycle after the burst read
operation completed. tRPST from the last falling edge of the data strobe, the DQS pins become High-Z. This low
period of DQS is referred as read postamble.
t0
t1
t2
t3
t4
t5
t6
t7
t8
CK
/CK
tRCD
NOP
Command
Address
NOP
ACT
Row
READ
NOP
Column
tRPRE
out0 out1
BL = 2
tRPST
DQS
DQ
out0 out1 out2 out3
BL = 4
BL = 8
out0 out1 out2 out3 out4 out5 out6 out7
CL = 2
BL: Burst length
Read Operation (Burst Length)
Preliminary Data Sheet E0237E30 (Ver. 3.0)
24
ELPIDA [ ELPIDA MEMORY ]
