MT47H128M16RT-25EIT Datasheet, PDF (79/134 Pages) Micron Technology – 2Gb: x4, x8, x16 DDR2 SDRAM Features

2Gb: x4, x8, x16 DDR2 SDRAM
Mode Register (MR)
Burst Type
Accesses within a given burst may be programmed to be either sequential or inter-
leaved. The burst type is selected via bit M3, as shown in Figure 36. The ordering of ac-
cesses within a burst is determined by the burst length, the burst type, and the starting
column address, as shown in Table 41. DDR2 SDRAM supports 4-bit burst mode and 8-
bit burst mode only. For 8-bit burst mode, full interleaved address ordering is suppor-
ted; however, sequential address ordering is nibble-based.
Table 41: Burst Definition
Burst Length
4
8
Starting Column Address
(A2, A1, A0)
00
01
10
11
000
001
010
011
100
101
110
111
Order of Accesses Within a Burst
Burst Type = Sequential
Burst Type = Interleaved
0, 1, 2, 3
0, 1, 2, 3
1, 2, 3, 0
1, 0, 3, 2
2, 3, 0, 1
2, 3, 0, 1
3, 0, 1, 2
3, 2, 1, 0
0, 1, 2, 3, 4, 5, 6, 7
0, 1, 2, 3, 4, 5, 6, 7
1, 2, 3, 0, 5, 6, 7, 4
1, 0, 3, 2, 5, 4, 7, 6
2, 3, 0, 1, 6, 7, 4, 5
2, 3, 0, 1, 6, 7, 4, 5
3, 0, 1, 2, 7, 4, 5, 6
3, 2, 1, 0, 7, 6, 5, 4
4, 5, 6, 7, 0, 1, 2, 3
4, 5, 6, 7, 0, 1, 2, 3
5, 6, 7, 4, 1, 2, 3, 0
5, 4, 7, 6, 1, 0, 3, 2
6, 7, 4, 5, 2, 3, 0, 1
6, 7, 4, 5, 2, 3, 0, 1
7, 4, 5, 6, 3, 0, 1, 2
7, 6, 5, 4, 3, 2, 1, 0
Operating Mode
The normal operating mode is selected by issuing a command with bit M7 set to “0,”
and all other bits set to the desired values, as shown in Figure 36 (page 78). When bit M7
is “1,” no other bits of the mode register are programmed. Programming bit M7 to “1”
places the DDR2 SDRAM into a test mode that is only used by the manufacturer and
should not be used. No operation or functionality is guaranteed if M7 bit is “1.”
DLL RESET
DLL RESET is defined by bit M8, as shown in Figure 36. Programming bit M8 to “1” will
activate the DLL RESET function. Bit M8 is self-clearing, meaning it returns back to a
value of “0” after the DLL RESET function has been issued.
Anytime the DLL RESET function is used, 200 clock cycles must occur before a READ
command can be issued to allow time for the internal clock to be synchronized with the
external clock. Failing to wait for synchronization to occur may result in a violation of
the ^tAC or ^tDQSCK parameters.
PDF: 09005aef824f87b6
2Gb_DDR2.pdf – Rev. H 10/11 EN
79
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