
SEC ASIC
5-11
STD80/STDM80
DROM Gen
Diffusion Programmable Synchronous ROM Generator
Pin Descriptions
Name
CK
Pin Capacitance
(Unit = SL)
DOUT
44.0
44.0
Application Notes
1)
Aspect ratio is programmable using low address decoder types. As you can see in the configuration table,
there are up to 3 selections of Ymux for the same Words and the same Bpw DROM. You can choose one of
them in accordance with your chip level layout preference. Larger Ymux means fatter and shorter aspect
ratio and smaller Ymux means thinner and taller aspect ratio. As you can see in the characteristic tables,
aspect ratio affects major characteristics of DROM, In general, larger Ymux DROM has faster speed and
bigger area than smaller Ymux DROM.
Customizing Aspect Ratio
2)
To enlarge the capacity of DROM, we added one more option to choose number of banks. If you want to use
larger DROM than 256K bit DROM, you can select dual bank (ba = 2). You can also select dual bank for
smaller one than 256K bit DROM. Dual bank DROM is a little bigger and a little faster than single bank one.
(Please refer to the characteristic tables.)
Selecting Number of Banks
I/O
I
Description
“Clock” serves as the input clock to the memory block. When CK is low the memory
is in a precharge state. Upon the rising edge, an access cycle begins.
“Chip Select Negative” acts as the memory enable signal for selections of multiple
blocks on a common clock. When CSN is high, the memory goes to stand-by (power
down) mode and no access to the memory can occur, conversely, if low only then
may a read access occur. CSN may not change during CK is high.
“Output Enable Negative” unconditionally controls the output drivers from driven to
tri-state condition.
“Address” selects the location to be accessed. A [ ] may not change during CK is
high.
During a read access, data word programmed will be presented to the “Data Out”
ports. DOUT [ ] is latched during a full cycle. When CSN is low and OEN is low, only
then, DOUT [ ] drives a certain value. Otherwise, DOUT [ ] keeps Hi-Z state.
CSN
I
OEN
I
A [ ]
I
DOUT [ ]
O
CK
2.1
4.2
CSN
0.6
1.2
OEN
1.1
2.2
A
2.3
2.3
1-bank
2-bank