H5GQ2H24AFR-R0C datasheet(81/172 Pages) HYNIX

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Rev. 1.2 /Nov. 2011

H5GQ2H24AFR

5.8. WRITE DATA MASK (DM)

The traditional method of using a DM pin for WRITE data mask must be abandoned for a new method.

Due to the high data rate of GDDR5 SGRAMs, bit errors are expected on the interface and are not recover‐

able when they occur on the traditional DM pin.

In GDDR5 the DM is sent to the SGRAM over the address following the bank/column address cycle associ‐

ated with the command, during the NOP/DESELECT commands between the WRITE command and the

next command. The DM is used to mask the corresponding data according to the following table.

Two additional WRITE commands that augment the traditional WRITE Without Mask (WOM) are

required for proper DM support:

•WDM: WRITE‐With‐Doublebyte‐Mask:

2 cycle command where the 1st cycle carries address information and the 2nd cycle carries data mask

information (2 byte granularity);

Table 17: DM State

FUNCTION

Value

Write Enable

Valid

Write Inhibit

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