All things in all posts will help you visualize about the way that computers work generally. Note that it is not the real structure of modern computers, but the way that modern computers work is nearly the same as in my posts. I am sure that if you understand about the way that computers work in my posts, you will easy to learn about all fields of computer afterward. Thank you !!!
The “bus 1” device is quite similar to the enabler device. It will decide whether the byte of data on the bus can go through it. The differences between “bus 1” and enabler are about structure and the byte of “00000001” is created when a byte of data can not go through this “bus 1” device. Let’s look at the diagram below to understand:
In the diagram, you can see one byte input, one byte output and one bit “bus 1”. The byte input will be the byte of data on the bus. When the “bus 1” bit is “1” (on), the byte of data will go through the “bus 1” device to become the byte output. But, when the “bus 1” bit is “0” (off), the byte output will be “00000001”. We have a value of “1” when this device is off, so this device is called “bus 1” device.
This device will be integrated into the CPU (central processing unit). Now, we will have a more complete diagram for CPU. Let’s look at the diagram below to see that thing:
Now, we will briefly mention the way that CPU works. Firstly, we will come to the case that we have one input ALU operation. The “e” bit of one register will be set “on” to allow byte of data transport on the common bus. Then, choosing the ‘op’ code for ALU operation on that byte of data. Finally, save the result into the “ACC” register by setting “s” bit “on”.
Secondly, we will come to the case that we have two inputs ALU operation. One register will be enabled first for byte of data on the bus, set the “TMP” register for saving that byte of data. Then, another register will be enabled for byte on the bus, choose the ‘op’ code for ALU operation on those two bytes. Finally, setting the result into the “ACC” register.
You can see that from the “ACC” register, we can enable it to transport result bytes of data on the bus. Then, we can set that byte to registers or RAM. Note that the primary byte for ALU operation can also be enabled from RAM. Maybe you will wonder how the CPU knows all steps that need to perform calculation exactly?
Yeah! That's based on the function of the control unit. As you can see on the diagram this unit controls all control bits of the CPU by connections to them. It controls “s” and “e” bits of R0, R1, R2, R3, TMP, ACC registers, RAM and MAR of RAM to control the time that is for setting and enabling them. It also controls the “bus 1” bit to enable byte of data on the bus, the ‘op’ bit for ALU operation on byte inputs.
In this post, I briefly mentioned some steps that CPU performs for ALU operations. You also have basic knowledge about the way that CPU works. In the next posts, we will discover the important structure of the CPU , the control unit. This is an interesting part that helps the CPU work step by step smoothly and exactly.
Hope you like this post. Thanks for reading and see you later!!!
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