8251 UART Microprocessor and Interfacing by Ravinder Nath Rajotiya - November 11, 2020May 10, 20210 The click for PPT is : L-31 Interfacing UART 8251-1
8279 Keyboard/Display Interface Microprocessor and Interfacing by Ravinder Nath Rajotiya - April 5, 2020April 25, 20220 Keyboard Types Mechanical key switches Membrane type: with advantage that they can be made very thin and sealed Capacitive Type: When a key is pressed the capacitance between the plates varies. Hall effect: No mechanical contact. It take advantage of the deflection of a moving charge by a magnetic field. Keyboard Circuit connection and Interfacing Detect a key press De-bounce the key press Encode the valid key to produce a standard code for pressed key The above three tasks can be performed with hardware, software or a combination depending on the application Keyboard interfacing Figure show the interfacing of the keypad using 8255. The rows of the keypad are connected to say PORT-A and columns connected to PORT-B. PA is in
8259 Priority Interrupt Controller Microprocessor and Interfacing by Ravinder Nath Rajotiya - March 27, 2020May 6, 20220 8259 Programmable Interrupt Controller The Intel 8259A programmable Interrupt Controller (PIC) is one of the most common interrupt controller used in IBM PCs. It can handle eight vectored priority interrupts for the CPU. It is a 28 pin DIP package and requires a single +5V DC supply for its operation. It is designed to minimize the software and real time overhead in handling multi-level priority interrupts. It has several modes, permitting optimization for a variety of system requirements. The pin diagram of 8259A is shown in figure-1 below. PIN Number Pin Name Description 1 CS’ Chip Select Input 2 WR’ Write control signal 3 RD’ Read control signal 4-11 D7-D0 Data Bus 12-13, 15 CAS0, CAS1 Cascade control 14 GND Ground 16 SP’/EN’ 17 INT Interrupt output for processor 18-25 IRQ0 – IRQ7 Interrupt request inputs 26 INTA Interrupt Acknowledge input 27 A0 Address input 28 VCC +5V supply 8259 interrupt Overview If the 8086 interrupt flag is set and INTR
Introduction to Interrupt System Microprocessor and Interfacing by Ravinder Nath Rajotiya - March 27, 2020April 6, 20200 Interrupts Interrupt is one of the most common methods for an external device to communicate with the processor. In small systems, for example, we might read ASCII characters on interrupt basis, count interrupt from a timer to produce real time clock or seconds, minutes and hours; detect several emergency conditions on interrupt basis. Figure-1 below shows a general concept of the interrupt in our day-to-day activity. Suppose we are enjoying listening to music, if now phone bell rings, we stop or pauses our music and attends the phone, after conversation is completed, we again restart the paused audio and continue to listen the music. We would not our audio every minute to check if phone bell is ringing, which would be an inefficient
8255 PPI(Programmable Peripheral Interface) Microprocessor and Interfacing by Ravinder Nath Rajotiya - March 26, 2020April 21, 20220 8255 Programmable Peripheral Interface 8255 is a programmable peripheral interface IC which is used as an interface between the external device and the microprocessor for parallel communication. This IC is a 40-pi IC having three ports known as Port-A(PA), Port-B(PB) and Port-C(PC). these ports can operate in various modes. the complete details is given in the following PPTSs. Features of the 8255: It provide three I/O ports All the three I/O ports are latched Port operation is configurable by programming 8255 i.e. writing a control word in CWR BSR- bit set-reset mode allows individual pins of port C to be controlled to be set or reset. PIN diagram of 8255 8255 PPI is a 40-pin IC, it has three 8-bit ports named PA, PB