In the previous post I explained how to make single bit memory circuit using relays. In a computer however, we want to deal with larger numbers not just 0 and 1. So, we can have N 1 bit memory units side by side and consider them as a single N bit number. The more bits you have clubbed together the larger a number we can store. For ease of explaining lets just consider four 1 bit memory units together.
These four bits can together can also be called a "4 bit register". The right most bit with the lowest place value is called the LSB (Least Significant Bit) and the left most bit having the highest place value is called the MSB (Most Significant Bit).
Now, with this four bit memory unit we can save any number from 0 to 15 i.e., from 0000 to 1111.
A memory register is of no use if it does not have DATA lines for us to read from or write to, so lets add them first...
In order to read and write to the register we also require read and write control lines. This is how they work:
When the Read line is pulled HIGH (connected to 12V), the register saves the data available on the Data lines.
When the Write line is pulled HIGH (connected to 12V), the Data in the register is available on the Data lines.Now, we can try and connect multiple register Data lines together via a set of conductors...
This set of conductors connecting multiple registers together are called the 'Bus'. Since, they connect the Data lines hence, its called the 'Data Bus'. What is great about this configuration is that the Data Bus allows us to copy data from one register to another. For example, if you want to transfer data from register 'A' to register 'B' just switch ON 'A' register's write and 'B' register's read line. In this way A with write to the bus and B will read from the bus and hence, the data gets copied from A to B.Using the concept of the Data Bus we can connect any number of circuits together.In this post I have only explain the system at a theoretical level and not the internal circuitry. The detailed circuits will be shared in future posts. till then....Got any queries???E-Mail me at: shashwath.sundar@gmail.com
These four bits can together can also be called a "4 bit register". The right most bit with the lowest place value is called the LSB (Least Significant Bit) and the left most bit having the highest place value is called the MSB (Most Significant Bit).Now, with this four bit memory unit we can save any number from 0 to 15 i.e., from 0000 to 1111.
A memory register is of no use if it does not have DATA lines for us to read from or write to, so lets add them first...
In order to read and write to the register we also require read and write control lines. This is how they work:
When the Write line is pulled HIGH (connected to 12V), the Data in the register is available on the Data lines.Now, we can try and connect multiple register Data lines together via a set of conductors...
This set of conductors connecting multiple registers together are called the 'Bus'. Since, they connect the Data lines hence, its called the 'Data Bus'. What is great about this configuration is that the Data Bus allows us to copy data from one register to another. For example, if you want to transfer data from register 'A' to register 'B' just switch ON 'A' register's write and 'B' register's read line. In this way A with write to the bus and B will read from the bus and hence, the data gets copied from A to B.Using the concept of the Data Bus we can connect any number of circuits together.In this post I have only explain the system at a theoretical level and not the internal circuitry. The detailed circuits will be shared in future posts. till then....Got any queries???E-Mail me at: shashwath.sundar@gmail.com
Comments
Post a Comment