EM638165
EtronTech
15 Clock Suspend Mode Entry / PowerDown Mode Entry command (CKE = "L")
When the SDRAM 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 all 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 (64ms) since the command does not perform any refresh operations.
16 Clock Suspend Mode Exit / PowerDown Mode Exit command (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", the command should be NOP or
deselect). 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.
17 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.
Rev. 5.2
16
Rev. 5.2
Dec. /2013
ETRON [ ETRON TECHNOLOGY, INC. ]
