Datasheet

CK#
CK
DON'T CARE
DRAM
(Internal)
CLK
CS#
CMD
CKE
1N Sync Pulse
2N Mode
Reset
NOTE 1. CKE High Assert to Gear Down Enable Time (tXS, tXS_Abort) depend on MR setting. A correspondence of tXS/tXS_Abort and MR Setting is as follows.
- MR4[A9] = 0 : tXS
- MR4[A9] = 1 : tXS_Abort
NOTE 2. Command not requiring locked DLL
NOTE 3. Only DES is allowed during tSYNC_GEAR
MRS NOP
VALID
2
t
XS or Abort
1
t
SYNC_GEAR
t
CMD_GEAR
t
GEAR_setup
t
GEAR_hold
Configure DRAM
to 1/4 rate
t
GEAR_setup
t
GEAR_hold
SRX
TdkN TdkN + Neven
t
DLLK
Figure 40. Gear down (2N) mode entry sequence after self refresh exit (SRX)
DESACT DES DES DES READ DES DES DES DES DES
NOTE 1. BL=8, tRCD=CL=16
NOTE 2. Dout n = data-out from column n.
NOTE 3. DES commands are shown for ease of illustration; other commands may be valid at these times.
NOTE 4. CA Parity = Disable, CS to CA Latency = Disable, Read DBI = Disable.
T0 T1 T2 T3 T15 T16 T17 T18 T30 T32
T33
CK#
CK
DQ
CL = t
RCD
= 18
CMD
AL = 0
(Geardown = Disable)
DES DES DES DES DES
DQ
Dout
n+1
Dout
n+2
Dout
n+3
Dout
n+4
Dout
n+5
Dout
n+6
Dout
n
Dout
n+7
Dout
n+1
Dout
n+2
Dout
n+3
Dout
n+4
Dout
n+5
Dout
n+6
Dout
n
Dout
n+7
DQ
Dout
n+1
Dout
n+2
Dout
n+3
Dout
n+4
Dout
n+5
Dout
n+6
Dout
n
Dout
n+7
READACT DES DES DES DES DES DES DES DES DES DES DES DES DES DES
ACT READ DES DES DES DES DES DES DES
T34 T35 T36 T37 T38
CMD
AL = CL - 1
(Geardown = Disable)
CMD
READ
READ
CL = RL = 16 (AL=0)
AL + CL = RL = 31 (AL = CL-1=15)
AL + CL = RL = 30 (AL = CL-2=14)
DON'T CARETRANSITIONING DATATIME BREAK
Figure 41. Comparison Timing Diagram Between Geardown Disable and Enable
AS4C256M16D4
Confidential
- 56 of 201 -
Rev.1.0 Aug.2019