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SEC ASIC
5-73
STD80/STDM80
DPARAM Gen
Dual-Port Asynchronous RAM Generator
Pin Descriptions
Name
CSN
Pin Capacitance
CSN
(Unit = SL)
Application Notes
1)
Layout Shape can be fitted by choosing one of 4 Ymux parameters in the above configuration table in
accordance with your chip level layout design preference. Larger one makes the layout shape flat and short.
Smaller one makes it thin and tall. In general, flat and short DPARAM is faster than thin and tall one.
Fitting the Layout Shape (Aspect Ratio)
2)
Simultaneous accesses to the same location through both ports cause a contention. DPARAM has no
contention-preventing scheme. User has to take care of the contention modes. Please refer to the timing
diagrams of contention modes to get more information of contention modes.
Contention Modes
I/O
I
Description
"Chip Select Negative" acts as the memory enable signal for selecting one of
multiple memory blocks. When CSN is high, DOUT[ ] goes to Hi-Z state, the memory
goes to stand-by (power down) mode and no access to the memory can occur.
Conversely, if CSN is low only then may a read or write access occur. When CSN
falls, a read access is initiated. CSN should be stable when WEN is low.
"Write Enable Negative" selects the type of memory access. When WEN is high, the
SPARAM is in read mode. Otherwise, it is in write mode. Upon the rising edge of
WEN, a write access completed and a read access initiated. When WEN is low, A[ ]
and CSN should be stable.
"Output Enable Negative" unconditionally enables or disables the output drivers.
"Address" selects the location to be accessed. When A[ ] changes, the transition is
detected and the internal clock pulse will be generated. A[ ] should be stable when
WEN is low.
When WEN rises, the "Data In" word value is written to the location addressed.
During a read access, the data word stored will be presented to the "Data OUT"
ports. DOUT[ ] is tri-statable. When CSN is low and OEN is low, only then, DOUT[ ]
drives a certain value. Otherwise, DOUT[ ] keeps Hi-Z state. During a write access,
the data on DOUT is unpredictable.
WEN1
I
OEN1
A [ ]
I
I
D [ ]
DOUT [ ]
I
O
WEN
OEN
A
DI
DOUT
Ymux 4
Ymux 8
Ymux 16
Ymux 32
STD80/STDM80
11.4
4.9
0.8
4.9
2.4
6.0
13.2
27.5
56.0