8051 PINOUTS

Let's get started. At this point, I assume that you are already familiar with the concept of microcontrollers (specially the 8051) and have some rough idea about the internal architecture because I will avoid going into it. I will just stick to how-to-use tricks for the 8051. However, for a brief introduction, let me highlight the important aspects of it.

UPDATE: You can also click this link for an updated version of this post.

We all know that 8051 is an 8-bit microcontroller. Here is the pin out diagram for the 8051

As you can see, it has a total of 40 pins with following features

• 4 input/output ports ( each 8 bits or 1 byte )
• Except Port1, each port has some dual nature or functionality
• RXD/TXD for serial transmission
• Interrupts and Timers

The remaining PINS are just for powering up the device. I suppose we will talk about each of the feature listed above in detail. From now on, I will refer to the ports as P0, P1, P2 and P3. And they all have 8 pins for data transfer so the individual pins are named as

P0.0 - P0.7
P1.0 - P1.7
P2.0 - P2.7
P3.0 - P3.7

You are supposed to get familiar with the PIN out diagram above because you will need to refer to it every now and then but don't worry about it either. The more you practise, the better you will remember each PIN without even checking out the data sheet. And talking of its data sheet, here you go

PDF : AT89C51 Datasheet