參數(shù)資料
型號: EDX5116ABSE-3C-E
廠商: ELPIDA MEMORY INC
元件分類: DRAM
英文描述: 512M bits XDR DRAM (32M words ?16 bits)
中文描述: 32M X 16 RAMBUS, PBGA104
封裝: LEAD FREE, FBGA-104
文件頁數(shù): 52/78頁
文件大小: 3611K
代理商: EDX5116ABSE-3C-E
Preliminary Data Sheet E0643E30 (Ver. 3.0)
52
EDX5116ABSE
Write Masking
Figure 41 shows the logic used by the XDR DRAM device
when a write-masked command (WRM) is specified in a
COLM packet. This masking logic permits individual bytes of a
write data packet to be written or not written according to the
value of an eight bit write mask M[7:0].
In Figure 41, there are 16 sets of 16 bit signals forming the
D1[15:0][15:0] input bus for the Byte Mask block. These are
treated as 2x16 8-bit bytes:
D1[15][15:8]
D1[15][7:0]
...
D1[1][15:8]
D1[1][7:0]
D1[0][15:8]
D1[0][7:0]
The eight bits of each byte is compared to the value in the byte
mask field (M[7:0]). If they are not equal (NE), then the corre-
sponding write enable signal (WE) is asserted and the byte is
written into the sense amplifier. If they are equal, then the cor-
responding write enable signal (WE) is deasserted and the byte
is not written into the sense amplifier.
In the example of Figure 41, a WRM command performs a
masked write of a 64 byte data packet to all the memory
devices connected to the RQ bus (and receiving the com-
mand). It is the job of the memory controller to search the 64
bytes to find an eight bit data value that is not used and place it
into the M[7:0] field. This will always be possible because there
are 256 possible 8-bit values and there are only 64 possible val-
ues used in the bytes in the data packet.
Figure 41
Byte Mask Logic
Note that other systems might use a data transfer size that is
different than the 64 bytes per t
CC
interval per RQ bus that is
used in the example in Figure 41.
Figure 42 shows the timing of two successive WRM com-
mands in COLM packets. The timing is identical to that of two
successive WR commands in COL packets. The one difference
Byte Mask (WR)
S[0][7:0]
8
D1[0][7:0]
8
M[7:0]
Compare
8
NE
Dynamic Width Demux (WR)
16x16
16x16
Dynamic Width Mux (RD)
16x16
S[15:0][15:0]
16x16
D[15:0][15:0]
WIDTH[2:0]
SC[3:0]
WIDTH[2:0]
SC[3:0]
4+3
4+3
Q[15:0][15:0]
D1[15:0][15:0]
16x16
M[7:0]
8
1
8
D1[0][7:0]
8
S[0][15:8]
8
D1[0][15:8]
8
Compare
8
NE
1
8
D1[0][15:8]
8
8
8
Compare
8
NE
1
8
D1[15][7:0]
8
8
8
Compare
8
NE
1
8
D1[15][15:8]
8
S[15][15:8]
WE-MSB
[15]
S[15][7:0]
D1[15][15:8]
D1[15][7:0]
WE-LSB
[15]
WE-MSB
[0]
WE-LSB
[0]
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