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define hrqthe hold demand output requests the access of the system bus in non- cascaded 8257 systems this is linked with hold pin of cpu in cascade
what is key bouncing mechanical switches are used as keys in lots of the keyboards when a key is pressed the contact bounce back and forth and settle
list the major components of the keyboarddisplay interfacea keyboard sectionb cpu interface sectionc display sectiond scan
what is the use of 8251 chip8251 chip is mostly used as the asynchronous serial interface among the processor and the external
what is an usartusart stands for universal synchronousasynchronous receiver transmitter it is a programmable communication interface that can
what is io mappingthe assignment of addresses to various io devices in the memory chip is known as io
what is memory mappingthe assignment of memory addresses to several registers in a memory chip is known as memory
what is interfacingan interface is a shared boundary among the devices which includes sharing information interfacing is the process of making two
what is the size of ports in 8255port-a 8-bitsport-cu 4-bitsport-b 8-bitsport-cl
what is the purpose of control word written to control register in 8255the control words written to control register state an io function for every
what is a control wordit is a word kept in a register control register used to control the operation of a program digital
list the operation modes of 8255a io modei mode 0-simple inputoutputii mode 1-strobed inputoutput handshake modeiii mode 2-strobed bidirectional
what is the function of mode set register in 8257the mode set register is used for programming the 8257 as per the needs of the system the function
what is the use of terminal count registereach of the four dma channels of 8257 has single terminal count register this 16-bit register is used for
what is the function of dma address registerevery dma channel has one dma address register the function of this register is to keep the address of
give the register organization of 8257the 8257 do the dma operation over four independent dma channels each of the four channels of 8257 has a couple
what is the use of modem control unit in 8251the modem control unit handles the modem handshake signals to coordinate the communication among the
what are the modes used in display modes1 left entry modein the left entry mode the data is going into from the left side of the display unit2 right
what are the modes used in keyboard modes1 scanned keyboard mode with 2 key lockout2 scanned keyboard particular error mode3 scanned keyboard with
what is the output modes used in 82798279 gives two output modes for selecting the display options1display scanin this mode 8279 gives 8 or 16
give the operating modes of 8259aa automatic rotationb end of interrupt eoic fully nested mode d automatic eoi modee specific rotationf edge and
input a list of positive numbers terminated by 0 into an array numbers then display the array and the largest and smallest number in
what are the different types of write operations used in 8253there are two types of write operations in 82531 writing a control word register2
what are the modes of operations used in 8253each of the three counters of 8253 can be operated in one of the following six modes of operation1 mode
what are the features used mode 2 in 8255the single 8-bit port in-group a is available1 the 8-bit port is bi-directional and additionally a 5-bit