STTS2004 datasheet(40/58 Pages) STMICROELECTRONICS

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Use in a memory module

STTS2004

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DocID024229 Rev 3

Use in a memory module

In the Dual In line Memory Module (DIMM) application, the SPD is soldered directly on to

the printed circuit module. The three slave address inputs (A0, A1, A2) must be connected

to VSS or VDD directly (that is without using a pull-up or pull-down resistor) through the

DIMM socket (see Table 25).

6.1

Programming the SPD

The SPD EEPROM can be programmed when:



the DIMM is isolated (not inserted on the PCB motherboard)



the DIMM is inserted on the PCB motherboard

6.1.1

Isolated DIMM

With specific programming equipment, it is possible to define the SPD EEPROM content

using byte and page write instructions, and to set its write-protection using the SWPn and

CWP instructions. To issue the SWPn and CWP instructions, the DIMM must be inserted in

the application-specific slot where the A0 signal must be driven to VHV during the whole

instruction. This programming step is mainly intended for use by DIMM makers, whose end-

application manufacturers will want to clear this write-protection with the CWP on their own

specific programming equipment, to modify the protection bytes.

The read protection status (RPSn), Set SPD Page address (SPAn), and the Read SPD

Page Address (RPA) commands are fully supported when the DIMM is isolated.

Table 25. DRAM DIMM connections

DIMM position

VSS (0)

VSS(0)

VSS (0)

VDD (1)

VSS (0)

VDD (1)

VSS (0)

VDD (1)

VDD(1)

VDD (1)

VSS (0)

VDD (1)

VSS (0)

VDD (1)

VSS (0)

VDD (1)

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