HY5FS123235AFCP Datasheet, PDF (50/74 Pages) Hynix Semiconductor – 512M (16Mx32) GDDR4 SDRAM

HY5FS123235AFCP
Data Terminator Disable (BUS SNOOPING FOR READ COMMANDS)
Bus snooping for READ commands is used to control the on-die termination in the dual load configuration.
The GDDR4 SDRAM will disable the on-die termination when a READ command is detected, regardless of the state of
CS#, when the ODT for the DQ pins are set for dual loads.
The on-die termination is disabled x clocks after the READ command where x equals CL - 1 and stay off for a duration
of BL + 2. In a two-rank system, both DRAM devices snoop the bus for READ commands to either device and both will
disable the on-die termination if a READ command is detected. The on-die termination for all other pins on the device
are always on for both a single-rank system and a dual-rank system.
Figure 36: Data Terminator Disable Timing
T0
CK#
CK
T1
T13
T14 T14n T15 T15n T16 T16n T17 T17n T18
T19
COMMAND READ
NOP
NOP
NOP
NOP
NOP
NOP
NOP
NOP
ADDRESS
Bank a,
Col n
Col n
RDQS
RPRE=1
DQ
CL = 14
t_RPRE
DOn
t_RPST
DO
n+7
DM
DBIn
DO
n+7
DQ ODT ODT Enabled
DQ ODT Disabled
ODT Enabled
RDQS ODT ODT Enabled
RDQS ODT Disabled
ODT Enabled
Snoop ODT ODT Enabled
DQ, RDQS ODT Disabled
ODT Enabled
Notes
1. DO n = data-out from column n.
2. Three subsequent elements of data-out appear in the specified order following DO n.
3. Shown with nominal t_AC and t_DQSQ.
4. RDQS will start driving high one-half clock cycle prior to the first falling edge.
5. The Data Terminators are disabled starting at CL - 1 and the duration is BL + 2.
6. READs to either rank disable both ranks termination regardless of the logic level of CS#.
Rev. 1.2 /June. 2008
50