EtronTech
EM636327
17 SelfRefresh Entry command (refer to Figure 5 in Timing Waveforms)
(RAS# = "L", CAS# = "L", WE# = "H", DSF = "L", CKE = "L", BS, A0-A9 = Don't care)
The SelfRefresh is another refresh mode available in the SGRAM. It is the preferred refresh
mode for data retention and low power operation. Once the SelfRefresh command is registered, all
the inputs to the SGRAM become "don't care" with the exception of CKE, which must remain LOW.
The refresh addressing and timing is internally generated to reduce power consumption. The
SGRAM may remain in SelfRefresh mode for an indefinite period. The SelfRefresh mode is exited
by restarting the external clock and then asserting HIGH on CKE (SelfRefresh Exit command).
18 SelfRefresh Exit command (refer to Figure 5 in Timing Waveforms)
(CKE = "H", CS# = "H" or CKE = "H", RAS# = "H", CAS# = "H", WE# = "H")
This command is used to exit from the SelfRefresh mode. Once this command is registered,
NOP or Device Deselect commands must be issued for tRC(min.) because time is required for the
completion of any bank currently being internally refreshed. If auto refresh cycles in bursts are
performed during normal operation, a burst of 2048 auto refresh cycles should be completed just
prior to entering and just after exiting the SelfRefresh mode.
19 Clock Suspend Mode Entry / PowerDown Mode Entry command (refer to Figures 6, 7, and 8 in
Timing Waveforms)
(CKE = "L")
When the SGRAM is operating the burst cycle, the internal CLK is suspended(masked) from
the subsequent cycle by issuing this command (asserting CKE "LOW"). The device operation is held
intact while CLK is suspended. On the other hand, when both banks are in the idle state, this
command performs entry into the PowerDown mode. All input and output buffers (except the CKE
buffer) are turned off in the PowerDown mode. The device may not remain in the Clock Suspend or
PowerDown state longer than the refresh period (32ms) since the command does not perform any
refresh operations.
20 Clock Suspend Mode Exit / PowerDown Mode Exit command (refer to Figures 6, 7, and 8 in Timing
Waveforms)
(CKE= "H")
When the internal CLK has been suspended, the operation of the internal CLK is reinitiated
from the subsequent cycle by providing this command (asserting CKE "HIGH"). When the device is
in the PowerDown mode, the device exits this mode and all disabled buffers are turned on to the
active state. tPDE(min.) is required when the device exits from the PowerDown mode. Any
subsequent commands can be issued after one clock cycle from the end of this command.
21 Data Write / Output Enable, Data Mask / Output Disable command
(DQM = "L", "H")
During a write cycle, the DQM signal functions as a Data Mask and can control every word of
the input data. During a read cycle, the DQM functions as the controller of output buffers. DQM is
also used for device selection, byte selection and bus control in a memory system. DQM0 controls
DQ0 to DQ7, DQM1 controls DQ8 to DQ15, DQM2 controls DQ16 to DQ23, and DQM3 controls
DQ24 to DQ31. DQM masks the DQ's by a byte regardless that the corresponding DQ's are in a
state of write-per-bit masking or pixel masking. Each DQM0-3 corresponds to DQ0-7, DQ8-15,
DQ16-23, and DQ24-31.
Preliminary
1998
December
18
ETRON [ ETRON TECHNOLOGY, INC. ]
