Introduction of Asynchronous SRAM

The RAM,i.e Random Access Memory is a primary source of data storing memory device for the computers. This memory is available in 2 forms, named as – 

• SRAM(Static RAM)
• DRAM(Dynamic RAM)

Whereas the SRAM is also divided broadly into 2 forms, those are –

• Synchronous SRAM
• Asynchronous SRAM

In this article, we will study what is Asynchronous SRAM. A thing to note here is that the SDRAM,i.e the Synchronous Dynamic Random Access Memory is different than that of Async SRAM. 

Asynchronous SRAM : 

• First of all, let us see what is meant by asynchronous here. The devices that do not depend on external clock pulse for their working, these devices are called asynchronous devices, and the SRAM which does not depend on an external clock for its working is known as asynchronous SRAM.
• It uses latching circuitry, which in particular is used by flip flops. As this SRAM does not depend on any external clock pulse, so as soon as it receives the instruction, it can read, write according to the instruction requirement. 
• It is usually preferred to be used as small cache embedded processors. It comes under the volatile memory, as it can store the value as long as the power is constantly supplied to the system. So the data in the Async SRAM is very volatile in nature.DRAM stores data as a charge on the capacitor. 
• The circuit architecture used for building the Async SRAM is complex in nature, so the number of components used for building its topology will be more, and this factor makes SRAM(S) more expensive than DRAM(S). In lots of home computers, DRAMS are used, like DDR3, DDR5, etc. 
• Now, as the data is getting stored statically in this SRAM, so the power required by the SRAM is less as compared to DRAM. SRAM(S) are storing data statically, so this makes them faster as compared to DRAM for storing data.

States of Asynchronous SRAM :

It can be in 3 states, namely – 

• Standby – It is a condition in SRAM when SRAM’s circuitry is sitting idle and no work is given to a particular SRAM. It can underutilize the capacity of the resources available.
• Reading – It is a condition in SRAM when the data has been requested to be fetched. It puts the SRAM’s circuitry in working condition.
• Writing – It is a c condition in SRAM when the data has to be updated or overwritten stored in Async SRAM. This state will also put SRAM’s circuitry in working condition.

Applications of Asynchronous SRAM :

• It is widely used in making CPU cache memory, hard drive buffers, etc which are mostly found as small memory applications.
• For manufacturing of the network equipment, the Asynchronous SRAM is very frequently used in the hardware implementation of the network equipment. Examples can be switches, routers, etc.
• Asynchronous SRAM(s) are used in the design of PLC, which is Programmable Logic Controllers.
• It is used in printers that have multiple features in them.

Advantages of Asynchronous SRAM :

• As Asynchronous SRAM(s) are having three states for their operation, so the communication of the Async SRAM becomes very effective in nature.
• The functionality of Async SRAM to perform fast makes it a preferred option in implementing in the network architecture.

While the Asynchronous SRAM seems to be the best option for usage, it also holds some disadvantages too. Some of them are as follows.

Disadvantages of Asynchronous SRAM :

• The cost for implementing Async SRAM is costlier, making it expensive for embedding in our systems.
• Asynchronous dual ports are generally slower than synchronous dual ports.
• The bandwidth capability of asynchronous SRAM is less than that of synchronous SRAM.