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STD80/STDM80
5-18
SEC ASIC
SPSRAM Gen
Single-Port Synchronous RAM Generator
Pin Descriptions
Name
CK
Pin Capacitance
(Unit = SL)
Application Notes
1)
As you will see in the timing diagrams, DOUT [ ] is valid only when CK is high. If you want DOUT [ ] to be
stable regardless of CK state, you should put STD80/STDM80 Busholder cells on the DOUT [ ] bus
externally.
Putting Busholders on DOUT [ ]
2)
Aspect ratio is programmable using low address decoder types. As you can see in the configuration table,
there are up to 5 selections of Ymux for the same Words and the same Bpw SPSRAM. 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 SPSRAM, In general, larger Ymux SPSRAM has faster speed
and bigger area than smaller Ymux SPSRAM.
Customizing Aspect Ratio
3)
To enlarge the capacity of SPSRAM, we added one more option to choose number of banks. If you want to
use larger SPSRAM than 64K bit SPSRAM, you can select dual bank (ba = 2). You can also select dual
bank for smaller one than 64K bit SPSRAM. Dual bank SPSRAM 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 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 or write access occur. CSN may not change during CK is high.
“Write Enable Negative” selects the type of memory access. Read is the high state,
and write is the low state.
“Output Enable Negative” controls the output drivers from driven to tri-state
condition. OEN may not change during CK is high.
“Address” selects the location to be accessed. A [ ] may not change during CK is
high.
When CK rises while WEN is low, the “Data In” word value is written to the accessed
location.
During a read access, data word stored will be presented to the “Data Out” ports.
DOUT [ ] is tri-statable. When CK is high, CSN is low and OEN is low, only then,
DOUT [ ] drives a certain value. Otherwise, DOUT [ ] keeps Hi-Z state. During a
write access, data word written will be presented at the “Data Out” ports if output
driver is enabled.
CSN
I
WEN
I
OEN
I
A [ ]
I
DI [ ]
I
DOUT [ ]
O
CK
CSN
WEN
OEN
A
DI
DOUT
Ymux 8
7.7
7.7
Ymux 2
3.1
3.1
Ymux 4
3.3
3.3
Ymux 16 Ymux 32
15.0
15.0
1-bank
2-bank
3.5
7.0
1.0
2.1
0.5
1.0
1.6
3.1
1.2
1.2
2.1
2.1
31.0
31.0