1Gb: x4, x8, x16 DDR3 SDRAM
READ Operation
Figure 01 (page 162). DDR3 SDRAM does not allow interrupting or truncating any
READ burst.
Data from any READ burst must be completed before a subsequent WRITE burst is al-
lowed. An example of a READ burst followed by a WRITE burst for BL8 is shown in Fig-
ure 02 (page 162) (BC4 is shown in Figure 03 (page 163)). To ensure the READ data is
completed before the WRITE data is on the bus, the minimum READ-to-WRITE timing
is RL + tCCD - WL + 2tCK.
A READ burst may be followed by a PRECHARGE command to the same bank, provided
auto precharge is not activated. The minimum READ-to-PRECHARGE command spac-
ing to the same bank is four clocks and must also satisfy a minimum analog time from
the READ command. This time is called tRTP (READ-to-PRECHARGE). tRTP starts AL
cycles later than the READ command. Examples for BL8 are shown in Figure 04
(page 163) and BC4 in Figure 05 (page 164). Following the PRECHARGE command, a
subsequent command to the same bank cannot be issued until tRP is met. The PRE-
CHARGE command followed by another PRECHARGE command to the same bank is al-
lowed. However, the precharge period will be determined by the last PRECHARGE com-
mand issued to the bank.
If A1± is HIGH when a READ command is issued, the READ with auto precharge func-
tion is engaged. The DRAM starts an auto precharge operation on the rising edge, which
is AL + tRTP cycles after the READ command. DRAM support a tRAS lockout feature (see
Figure 00 (page 164)). If tRAS (MIN) is not satisfied at the edge, the starting point of the
auto precharge operation will be delayed until tRAS (MIN) is satisfied. If tRTP (MIN) is
not satisfied at the edge, the starting point of the auto precharge operation is delayed
until tRTP (MIN) is satisfied. In case the internal precharge is pushed out by tRTP, tRP
starts at the point at which the internal precharge happens (not at the next rising clock
edge after this event). The time from READ with auto precharge to the next ACTIVATE
command to the same bank is AL + (tRTP + tRP)*, where * means rounded up to the next
integer. In any event, internal precharge does not start earlier than four clocks after the
last 8n-bit prefetch.
PDF: 09005aef826aa906
1Gb_DDR3_SDRAM.pdf - Rev. L 03/13 EN
Micron Technology, Inc. reserves the right to change products or specifications without notice.
160
2006 Micron Technology, Inc. All rights reserved.
MICRON [ MICRON TECHNOLOGY ]
