Month: June 2011

Addressing 5 ROM Chips, Each of 4 KB Using 74LS138 Decoder: The following diagram is representing the addressing of 5 ROM chips using 74LS138 where each chip is of 4 KB. Explanation: From the previously given figure 01 it can be found that the Chip Select (CS) of the 5 ROM chips has been attached … Read more

Interfacing the Microprocessor with Analog World: As computer used digital binary values whereas we have physical variables, a step by step process is used to convert the physical variable to binary data and again to physical variable. The figure is given below,             (i) Transducer: A transducer is a device that … Read more

Controlling LEDs Using Microprocessor VIA 82C55A: Using the 82C55A, we can control LED lights. We can use the pins of one port to connect with one leg of the LEDs and pins of another port to connect rest of the legs. Then we can program the 82C55A to control the LEDs. It can be done … Read more

Purpose of Using Command Byte A: Command byte A is used select modes, working functions of the ports. So the importance of using command byte A is that we can define on which mode it will be working on and which port will be used for which function such as input or output. For example, … Read more

The given bit format is as follows, 7 6 5 4 3 2 1 0 1 0 0 0 0 0 1 0 Arrangement of Ports Due to Given Bit Format:             So the arrangement will be, mode 0, port A and C as output, port B as input.

(i) Required Bit Format of command byte A:            So the bit format will be 10010000.           (ii) Required Bit Format of command byte A:  So the bit format will be 1010×11×.

Command Byte A and Command Byte B:

Pin-Out Diagram of 82C55A: I/O Ports: It has three I/O ports, A, B and C. Each of these has 8 pins.             CS : This is used to select the 82C55A for programming and reading or writing.             A0 & A1: Register selection is done using the A0 and A1, which select … Read more

Handshaking:  Handshaking is a I/O control method to synchronize I/O devices with the microprocessor. As many I/O devices accepts or release information at a much slower rate than the microprocessor, this method is used to control the microprocessor to work with a I/O device at the I/O devices data transfer rate. Example:  Supposing that we … Read more

Memory Mapped I/O and Isolated I/O are two methods of performing input-output operations between CPU and installed peripherals in the system. Memory mapped I/O uses the same address bus to connect both primary memory and memory of hardware devices. Thus the instruction to address a section or portion or segment of RAM can also be used to address … Read more