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Samsung ASIC
5-129
STDL130
ARFRAM_HDL
High-Density Multi-Port Asynchronous Register File
Application Notes
1.
Permitting over-the-cell routing.
In ARFRAM_HDL, the over-the-cell routing is permitted for Metal-4 or upper layers. Namely, while doing
layout on the chip-level, any signals to be routed can be crossed over the area of register file generated
by ARFRAM_HDL compiler.
2.
Incoming power bus should be adjusted to guarantee NOT more than 10% voltage drop at typical-case
current levels.
3.
Power stripe should be tapped from both sides of ARFRAM_HDL.
4.
Contention mode under same addresses(RA[]=WA[] or WA0[] = WA1[]).
In ARFRAM_HDL, simultaneous operations by both ports on the same address(RA[]=WA[] or WA0[] =
WA1[]) such as read/write,write/read, write/write operation, cause a contention problem. Simultaneous
operations are defined as the state in which both ports are enabled and both address buses are equal.
ARFRAM_HDL has no scheme preventing the contention mode. Due to the simultaneous operations,
silicon will behave unpredictably. A write operation cannot completes and data appearing at outputs may
not be valid.
Please refer to the timing diagrams if you want to avoid the contention mode between both ports.
5.
Keeping the stable address cycle time in read mode.
In ARFRAM_HDL, rather than the write operation which is synchronously performed by CK signal, the
read operation is asynchronously performed whenever the address transition occures. So, in read
mode if the another transition on the address occures after first transition within access time, read
operation cannot completes. At that time, while in the read operation, the data stored in the memory
may be corrupted due to the short transition. To prevent such fail, the stable read address cycle time
(trcyc) is required. The essential requirement to recognize valid read address transition is that at least
minimum address period should be equal or greater than tacc (access time).
6.
Power reduction during standby mode.
ARFRAM_HDL provides two types of standby modes – the write standby mode and the read standby
mode. While in the write standby mode, WA[] and DI[] except CK are blocked even though the
transitions of those signals occure. While in the read standby mode, RA[] is blocked even though its
transition occures. So, you can reduce the power consumption in ARFRAM_HDL by properly using two
standby modes in your design.