Datasheet

DLL “off” to DLL “on” Procedure
To switch from DLL “off” to DLL “on” (with required frequency change) during Self-Refresh:
1. Starting from Idle state (All banks pre-charged, all timings fulfilled and DRAMs On-die Termination resistors
(R
TT_NOM
) must be in high impedance state before Self-Refresh mode is entered.)
2. Enter Self Refresh Mode, wait until t
CKSRE
satisfied.
3. Change frequency, following the guidelines in the Input Clock Frequency Change section.
4. Wait until a stable clock is available for at least (t
CKSRX
) at device inputs.
5. Starting with the Self Refresh Exit command, CKE must continuously be registered high until t
DLLK
timing
from subsequent DLL Reset command is satisfied. In addition, if any ODT features were enabled in the
mode registers when Self Refresh mode was entered, the ODT signal must continuously be registered low
until t
DLLK
timings from subsequent DLL Reset command is satisfied. If R
TT_NOM
were disabled in the mode
registers when Self Refresh mode was entered, ODT signal is don’t care.
6. Wait t
XS
or t
XS_ABORT
depending on Bit A9 in MR4, then set MR1 bit A0 to “1” to enable the DLL.
7. Wait t
MRD
, then set MR0 bit A8 to “1” to start DLL Reset.
8. Wait t
MRD
, then set Mode Registers with appropriate values (especially an update of CL, CWL and WR may
be necessary. After t
MOD
satisfied from any proceeding MRS command, a ZQCL command may also be
issued during or after t
DLLK
.)
9. Wait for t
MOD
, then device is ready for next command. (Remember to wait t
DLLK
after DLL Reset before
applying command requiring a locked DLL). In addition, wait also for t
ZQoper
in case a ZQCL command was
issued.
Tb0 Tb4 Tc Td Te0 Te1 Tf Tg ThTa
SRE
2
DES DES VALID
6
VALID
7
VALID
8
t
CKSRE
Notes 3
t
CKSRX
4
t
XS_ABORT
t
XS
t
CKESR
NOTES:
1. Starting with Idle State
2. Enter SR
3. Change Frequency
4. Clock must be stable t
CKSRX
5. Exit SR
6.7. Set DLL-on by MR1 A0=’1’
8. Start DLLReset
9. Update rest MR register values after t
DLLK
(not shown in the diagram)
t
MRD
t
IS
Exit Self Refresh
VALID VALID VALID
t
CPDED
t
IS
VALID
VALID VALID VALID VALID
Enter Self Refresh
CK#
CK
CMD
CKE
ODT
ADDR
t
RP
DON'T CARETIME BREAK
SRX
5
Figure 10. DLL Switch Sequence from DLL OFF to DLL ON
AS4C256M16D4
Confidential
- 29 of 201 -
Rev.1.0 Aug.2019