64Mb: x32
SDRAM
CONCURRENT AUTO PRECHARGE
An access command to (READ or WRITE) another
bank while an access command with auto precharge
enabled is executing is not allowed by SDRAMs, unless
the SDRAM supports CONCURRENT AUTO
PRECHARGE. Micron SDRAMs support CONCURRENT
AUTO PRECHARGE. Four cases where CONCURRENT
AUTO PRECHARGE occurs are defined below.
on bank n, CAS latency later. The PRECHARGE to
bank n will begin when the READ to bank m is regis-
tered (Figure 24).
2. Interrupted by a WRITE (with or without auto
precharge): A WRITE to bank m will interrupt a READ
on bank n when registered. DQM should be used
two clocks prior to the WRITE command to prevent
bus contention. The PRECHARGE to bank n will
begin when the WRITE to bank m is registered (Fig-
ure 25).
READ with auto precharge
1. Interrupted by a READ (with or without auto
precharge): A READ to bank m will interrupt a READ
Figure 24
READ With Auto Precharge Interrupted by a READ
T0
T1
T2
T3
T4
T5
T6
T7
CLK
READ - AP
BANK n
READ - AP
BANK m
NOP
NOP
NOP
NOP
NOP
NOP
COMMAND
Page Active
READ with Burst of 4
Interrupt Burst, Precharge
t
Idle
BANK n
t
RP - BANK n
RP - BANK m
Internal
States
Precharge
Page Active
READ with Burst of 4
BANK m
BANK n,
COL a
BANK m,
COL d
ADDRESS
DQ
D
a
OUT
D
a + 1
OUT
D
OUT
DOUT
d + 1
d
CAS Latency = 3 (BANK n)
CAS Latency = 3 (BANK m)
NOTE: DQM is LOW.
Figure 25
READ With Auto Precharge Interrupted by a WRITE
T0
T1
T2
T3
T4
T5
T6
T7
CLK
READ - AP
BANK n
WRITE - AP
BANK m
NOP
NOP
NOP
NOP
NOP
NOP
COMMAND
Page
Active
READ with Burst of 4
Page Active
Interrupt Burst, Precharge
t
Idle
WR - BANK m
BANK n
t
RP - BANK
n
Internal
States
Write-Back
WRITE with Burst of 4
BANK m
BANK n,
COL a
BANK m,
COL d
ADDRESS
1
DQM
D
OUT
DIN
d
D
d + 1
IN
D
d + 2
IN
DIN
d + 3
DQ
a
CAS Latency = 3 (BANK n)
NOTE: 1. DQM is HIGH at T2 to prevent DOUT-a+1 from contending with DIN-d at T4.
DON’T CARE
64Mb: x32 SDRAM
64MSDRAMx32_5.p65 – Rev. B; Pub. 6/02
MicronTechnology,Inc.,reservestherighttochangeproductsorspecificationswithoutnotice.
©2002,MicronTechnology,Inc.
23
MICRON [ MICRON TECHNOLOGY ]
