HM5225165B/HM5225805B/HM5225405B-75/A6/B6
DQM Truth Table (HM5225165B)
CKE
Command
Symbol
n - 1
H
n
×
×
×
×
DQMU DQML
Upper byte (DQ8 to DQ15) write enable/output enable ENBU
Lower byte (DQ0 to DQ7) write enable/output enable ENBL
Upper byte (DQ8 to DQ15) write inhibit/output disable MASKU
Lower byte (DQ0 to DQ7) write inhibit/output disable MASKL
L
×
H
×
×
L
×
H
H
H
H
Note: H: VIH. L: VIL. ×: VIH or VIL.
Write: IDID is needed.
Read: IDOD is needed.
DQM Truth Table (HM5225805B/HM5225405B)
CKE
n - 1
H
Command
Symbol
ENB
n
×
×
DQM
Write enable/output enable
Write inhibit/output disable
L
MASK
H
H
Note: H: VIH. L: VIL. ×: VIH or VIL.
Write: IDID is needed.
Read: IDOD is needed.
The SDRAM can mask input/output data by means of DQM, DQMU/DQML.
DQMU masks the upper byte and DQML masks the lower byte. (HM5225165B)
During reading, the output buffer is set to Low-Z by setting DQM, DQMU/DQML to Low, enabling data
output. On the other hand, when DQM, DQMU/DQML is set to High, the output buffer becomes High-Z,
disabling data output.
During writing, data is written by setting DQM, DQMU/DQML to Low. When DQM, DQMU/DQML is set
to High, the previous data is held (the new data is not written). Desired data can be masked during burst read
or burst write by setting DQMU/DQML. For details, refer to the DQM, DQMU/DQML control section of the
SDRAM operating instructions.
Data Sheet E0082H10
12
ELPIDA [ ELPIDA MEMORY ]
