KM416RD8AS-RBM80 datasheet(21/64 Pages) SAMSUNG

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Page 18

KM416RD8AS

Direct RDRAM™

Rev. 0.9 July. 1999

Target

Precharge Mechanisms

Figure 13 shows an example of precharge with the ROWR

packet mechanism. The PRER command must occur a time

tRAS after the ACT command, and a time tRP before the next

ACT command. This timing will serve as a baseline aginst

which the other precharge mechanisms can be compared.

Figure 14 (top) shows an example of precharge with a RDA

command. A bank is activated with an ROWA packet on the

ROW pins. Then, a series of four dualocts are read with RD

commands in COLC packets on the COL pins. The fourth of

these commands is a RDA, which causes the bank to auto-

matically precharge when the final read has finished. The

timing of this automatic precharge is equivalent to a PRER

command in an ROWR packet on the ROW pins that is

offset a time tOFFP from the COLC packet with the RDA

command. The RDA command should be treated as a RD

command in a COLC packet as well as a simultaneous (but

offset) PRER command in an ROWR packet when analyzing

interactions with other packets.

Figure 14 (middle) shows an example of precharge with a

WRA command. As in the RDA example, a bank is acti-

vated with an ROWA packet on the ROW pins. Then, two

dualocts are written with WR commands in COLC packets

on the COL pins. The second of these commands is a WRA,

which causes the bank to automatically precharge when the

final write has been retired. The timing of this automatic

precharge is equivalent to a PRER command in an ROWR

packet on the ROW pins that is offset a time tOFFP from the

COLC packet that causes the automatic retire. The WRA

command should be treated as a WR command in a COLC

packet as well as a simultaneous (but offset) PRER

command in an ROWR packet when analyzing interactions

with other packets. Note that the automatic retire is triggered

by a COLC packet a time tRTR after the COLC packet with

the WR command unless the second COLC contains a RD

command to the same device. This is described in more

detail in Figure 17.

Figure 14 (bottom) shows an example of precharge with a

PREX command in an COLX packet. A bank is activated

with an ROWA packet on the ROW pins. Then, a series of

four dualocts are read with RD commands in COLC packets

on the COL pins. The fourth of these COLC packets

includes an COLX packet with a PREX command. This

causes the bank to precharge with timing equivalent to a

PRER command in an ROWR packet on the ROW pins that

is offset a time tOFFP from the COLX packet with the PREX

command.

Figure 13: Precharge via PRER Command in ROWR Packet

CTM/CFM

DQA7..0

DQB7..0

COL4

..COL0

ROW2

..ROW0

T12

T13

T10

T14

T11

T15 T16

T20

T24

T28

T17

T21

T25

T29

T18

T22

T26

T30

T19

T23

T27

T31 T32

T36

T40

T44

T33

T37

T41

T45

T34

T38

T42

T46

T35

T39

T43

T47

ACT a0

PRER a5

tRAS

tRC

a0 = {Da,Ba,Ra}

a5 = {Da,Ba}

b0 = {Da,Ba,Rb}

tRP

ACT b0

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