EM639165
OPERATIONAL DESCRIPTION
READ
BANK ACTIVATE
After tRCD from the bank activation, a READ command can be
issued. 1st output data is available after the /CAS Latency from the
READ, followed by (BL -1) consecutive data when the Burst Length
is BL. The start address is specified by A0-A9,A11(x4), A0-9(X8),
A0-8(X16) , and the address sequence of burst data is defined by
the Burst Type. A READ command may be applied to any active
bank, so the row precharge time (tRP) can be hidden behind
continuous output data by interleaving the multiple banks. When
A10 is high at a READ command, the auto-precharge (READA) is
performed. Any command (READ, WRITE, PRE, TBST, ACT) to
the same bank is inhibited till the internal precharge is complete.
The internal precharge starts at BL after READA. (Need to keep
tRAS min.) The next ACT command can be issued after (BL +
tRP) from the previous READA.
The SDRAM has four independent banks. Each bank is activated by
the ACT command with the bank addresses (BA0,1). A row is indi-
cated by the row addresses A0-11. The minimum activation interval
between one bank and the other bank is tRRD. Maximum 2 ACT
commands are allowed within tRC , although the number of banks
which are active concurrently is not limited.
PRECHARGE
The PRE command deactivates the bank indicated by BA0,1. When
multiple banks are active, the precharge all command (PREA, PRE
+ A10=H) is available to deactivate them at the same time.
After tRP from the precharge, an ACT command to the same bank
can be issued.
Bank Activation and Precharge All (BL=4, CL=3)
CLK
2 ACT command / tRCmin
tRCmin
Command
A0-9
ACT
ACT READ
PRE
ACT
Xb
tRRD
tRAS
tRP
Xa
Xb
tRCD
Y
0
A10
Xa
Xb
Xb
01
1
Xb
A11
Xa
Xb
BA0,1
DQ
00
00
01
Qa0
Qa1 Qa2 Qa3
Precharge all
Preliminary
Rev 1.0 Feb. 2001
15
ETRON [ ETRON TECHNOLOGY, INC. ]
