HYS72D32000GR-7-B Datasheet, PDF (22/23 Pages) Infineon Technologies AG – 2.5 V 184-pin Registered DDR-I SDRAM Modules

HYS 72Dxx0xxGR-7/8-B
Registered DDR-I SDRAM-Modules
Although keeping the clocks running increases power consumption from the on-DIMM PLL during self refresh,
this is an alternate operating mode for these DIMMs.
1. System enters Self Refresh entry command.
(CKE→ Low, CS→ Low, RAS→ Low, CAS→ Low, WE→ High)
Note: The commands reach the DDR SDRAM one clock later due to the additional register pipelining on a
Registered DIMM. After this command is issued to the SDRAM, all of the address and control and clock input
conditions to the SDRAM are Don’t Cares — with the exception of CKE.
2. The system sets RESET at a valid low level.
This input condition forces all register outputs to a low state, independent of the condition on the data and
clock register inputs, and ensures that CKE is a stable low-level at the DDR SDRAMs.
3. The system may release DIMM address and control inputs to High-Z.
This can be done after the RESET deactivate time of the register (t (INACT) ). The deactivate time describes
the time in which the clocks and the control and the address signals must maintain valid levels after RESET
low has been applied. It is highly recommended that CKE continue to remain low during the operation.
4. The DIMM is in a low power, Self Refresh mode.
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 con-
nector).
CKE must be maintained low and all other inputs should be driven to a known state. In general these com-
mands 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.
2. The system switches RESET to a logic 'high' level.
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).
3. The system must maintain stable register inputs until normal register operation is attained.
The registers have an activation time that allows the clock receivers, input receivers, and output drivers suffi-
cient 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 out-
puts 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.
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
INFINEON Technologies
22
2002-09-10 (revision 0.91)