In our experiment, we were required to establish a serial communication link between an IBM-PC and 89C51 micro-controller, both having built-in serial ports. But, unfortunately, these two devices work at different voltage levels. IBM-PC serial port works on RS-232 levels whereas the micro-controller works on TTL logic levels. So, there was a need to convert these different logic levels to levels which become compatible with both the devices. So, two level converting ICs or line drivers have been used for this purpose.
The transmit line of PC’s serial port is connected to the receive line of 89C51 micro-controller and similarly, the transmit line of 89C51 micro-controller is connected to the receive line of PC’s serial port. Also, the ground signals of these two devices are made common. Line drivers are connected at the proper places to ensure correct voltage level conversions.
The following is the block diagram of the hardware circuit attached with the IBM-PC and 89C51 micro-controller.interfacing of 8051 with 4511
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