148
8.5.4
Byte Access Control
16-bit width and 18-bit width DRAMs require different types of byte control signals for access. By
setting the dual CAS signals/dual WE signals select bit (CW2) in DCR, the BSC allows selection
of either the dual CAS signal or dual WE signal system of control signals. When 16-bit space is
being accessed and the CW2 bit is cleared to 0 for dual CAS signals,
CASH
,
CASL
, and
WRL
signals are output; when CW2 is set to 1 for dual WE signals, the
CASL
,
WRH
, and
WRL
signals
are output. When accessing 8-bit space,
WRL
and
CASL
are output regardless of the CW2 setting.
Figure 8.21 shows the control timing of the upper byte write cycle (short pitch) in 16-bit space.
Summary of Contents for HD6417032
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Page 525: ...490 CK RAS CAS TRp TRc TRcc tRASD1 tRASD2 tCASD3 tCASD2 TRr tCSR Figure 20 18 Self Refresh ...
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