PC2700 INFINEON [Infineon Technologies AG], PC2700 Datasheet - Page 47

• Manufacturer Part Number: PC2700
• Description: 184 - Pin Registered Double Data Rate SDRAM Modules
• Manufacturer: INFINEON [Infineon Technologies AG]

Self Refresh Exit (RESET low, clocks running) — Optional
1. The system applies valid logic levels to the data inputs of the register (address and controls at the DIMM
2. The system switches RESET to a logic 'high' level.
3. The system must maintain stable register inputs until normal register operation is attained.
4. The system can begin JEDEC defined DDR SDRAM Self Refresh Exit Procedure.
Self Refresh Entry/Exit (RESET high, clocks running) — Optional
As this sequence does not involve the use of the RESET function, the JEDEC standard SDRAM specification
explains in detail the method for entering and exiting Self Refresh for this case.
Self Refresh Entry (RESET high, clocks powered off) — Not Permissible
In order to maintain a valid low level on the register output, it is required that either the clocks be running and the
system drive a low level on CKE, or the clocks are powered off and RESET is asserted low according to the
sequence defined in this application
the PLL drives a High-Z clock input into the register clock input. Without the low level on RESET an unknown DIMM
state will result.
Data Sheet
connector). CKE must be maintained low and all other inputs should be driven to a known state. In general
these commands can be determined by the system designer. One option is to apply an SDRAM ‘NOP’
command (with CKE low), as this is the first command defined by the Self Refresh Exit sequence (ideally this
would be a ‘NOP Deselect’ command). A second option is to apply low levels on all of the register inputs to be
consistent with the state of the register outputs.
The SDRAM is now functional and prepared to receive commands. Since the RESET signal is asynchronous,
it does not need to be tied to a particular clock edge (during this period, register inputs must continue to remain
stable).
The registers have an activation time that allows the clock receivers, input receivers, and output drivers
sufficient time to be turned on and become stable. During this time the system must maintain the valid logic
levels described in Step 1. It is also a functional requirement that the registers maintain a low state at the CKE
outputs in order to guarantee that the DDR SDRAMs continue to receive a low level on CKE. This activation
time, from asynchronous switching of RESET from low to high, until the registers are stable and ready to accept
an input signal, is t (ACT ) as specified in the register and DIMM documentation.
note.
In the case where RESET remains high and the clocks are powered off,
Registered Double Data Rate SDRAM Modules
47
HYS72D[32/64/128]3[00/20]GBR
10102003-01E2-HPA8
Application Note
Rev. 1.1, 2004-04