mt48lc4m32b2tg-7-it Micron Semiconductor Products, mt48lc4m32b2tg-7-it Datasheet - Page 24

• Manufacturer Part Number: mt48lc4m32b2tg-7-it
• Description: 128mb X32 Sdram
• Manufacturer: Micron Semiconductor Products

Figure 12:
Figure 13:
PDF: 09005aef80872800/Source: 09005aef80863355
128MbSDRAMx32_2.fm - Rev. K 9/07 EN
READ-to-WRITE
READ-to-WRITE with Extra Clock Cycle
Notes:
Notes:
COMMAND
1. CL = 3is used for illustration. The READ command may be to any bank, and the WRITE com-
The DQM input is used to avoid I/O contention, as shown in Figures 12 and 13. The
DQM signal must be asserted (HIGH) at least two clocks prior to the WRITE command
(DQM latency is two clocks for output buffers) to suppress data-out from the READ.
Once the WRITE command is registered, the DQs will go High-Z (or remain High-Z),
regardless of the state of the DQM signal; provided the DQM was active on the clock just
prior to the WRITE command that truncated the READ command. If not, the second
WRITE will be an invalid WRITE. For example, if DQM was low during T4 in Figure 13,
then the WRITEs at T5 and T7 would be valid, while the WRITE at T6 would be invalid.
The DQM signal must be de-asserted prior to the WRITE command (DQM latency is
zero clocks for input buffers) to ensure that the written data is not masked. Figure 12
shows the case where the clock frequency allows for bus contention to be avoided
without adding a NOP cycle, and Figure 13 shows the case where the additional NOP is
needed.
COMMAND
1. CL = 3 is used for illustration. The READ command may be to any bank, and the WRITE com-
ADDRESS
ADDRESS
mand may be to any bank. If a burst of one is used, then DQM is not required.
mand may be to any bank.
DQM
DQM
CLK
CLK
DQ
DQ
BANK,
COL n
BANK,
T0
COL n
T0
READ
READ
T1
T1
NOP
NOP
T2
T2
NOP
NOP
24
T3
T3
NOP
NOP
D
OUT
t HZ
t HZ
D
OUT
t CK
n
n
DON’T CARE
BANK,
Micron Technology, Inc., reserves the right to change products or specifications without notice.
T4
COL b
T4
WRITE
NOP
D
IN
b
t
DS
DON’T CARE
T5
BANK,
COL b
WRITE
D
IN
b
t
DS
©2001 Micron Technology, Inc. All rights reserved.
128Mb: x32 SDRAM
Register Definition