W641GG2JB Datasheet, PDF (49/109 Pages) Winbond – 1-Gbit GDDR3 Graphics SDRAM

W641GG2JB
1-Gbit GDDR3 Graphics SDRAM
6.7.7 Impedance Autocalibration of Output Buffer and Active Terminator
GDDR3 GRAPHICS SDRAMs offer autocalibrating impedance output buffers and on-die terminations (ODT). This enables auser to
match the driver impedance and terminations to the system within a given range. To adjust the impedance, an external precision
resistor shall be connected between the ZQ pin and VSSQ. A nominal resistor value of 240 is equivalent to 40 Pulldown, 40 Pullup
and 60 ODT nominal impedances. If no resistance is connected to the ZQ pin, a default value of 240 is assumed and no calibration
is performed.
The output driver and on-die termination impedances are updated during all REFRESH commands to compensate for variations in
supply voltage and temperature. The impedance updates are transparent to the system.
Table provides an overview of the ODT settings controlled by EMRS1.
6.7.7.1 Impedance Options
Signal
CLK,CLK#,RES,MF,SEN
CKE,CS0#,CS1#,RAS#,CAS#,WE#,BA0-
BA2,A0-A12
DM0-DM3,WDQS0-WDQS3
DQ0-DQ31
RDQS0-RDQS3
ODT Activation
No ODT
Always on
Always on
Always on except for Reads
(bus snooping)
No ODT
EMRS1 Control Bits
-
A8-A9
A2-A3
A2-A3
-
6.7.7.2 Timing of Vendor Code and Revision ID Generation on DQ[7:0]
0
1
2
3
4
5
6
7
8
9
10
CLK#
CLK
Com. EMRS
N/D
N/D
N/D
N/D
N/D
EMRS
N/D
N/D
N/D
N/D
A[9:0],A11 Add
A10
RDQS
tRIDon
Add
tRIDoff
DQ[7:0]
Vender Code and Revision ID
EMRS : Extended Mode Register Set Command
Add : Address
N / D : NOP or Deselect
Don‘t care
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Publication Release Date: Apr, 22, 2011
Revision A01-002