hm5216805 Renesas Electronics Corporation., hm5216805 Datasheet - Page 38

• Manufacturer Part Number: hm5216805
• Description: 16 M Lvttl Interface Sdram 100 Mhz/83 Mhz 1-mword 8-bit 2-bank/2-mword 4-bit 2-bank - Hitachi Semiconductor
• Manufacturer: Renesas Electronics Corporation.

HM5216805 Series, HM5216405 Series
DQM Control
The DQM mask the lower and upper bytes of the I/O data, respectively. The timing of DQM is different
during reading and writing.
Reading: When data is read, the output buffer can be controlled by DQM.
By setting DQM to Low, the output buffer becomes Low-Z, enabling data output. By setting DQM to
High, the output buffer becomes High-Z, and the corresponding data is not output. However, internal
reading operations continue. The latency of DQM during reading is 2.
Writing: Input data can be masked by DQM. By setting DQM to Low, data can be written. In addition,
when DQM is set to High, the corresponding data is not written, and the previous data is held. The latency
of DQM during writing is 0.
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I/O(output)
I/O(input)
DQM
DQM
CLK
CLK
out 0
in 0
l
DOD
= 2 Latency
out 1
in 1
l
DID
High-Z
= 0 Latency
out 3
in 3