The 8255 is a 40 pin integrated circuit ic, designed the 8255. The 825x chips or equivalent circuit embedded in a larger chip are found in all ibm pc. The 825x family was primarily designed for the intel 8080 8085. Write a program to initialize 8255 in the configuration below. It was first available in a 40pin dip and later a 44pin plcc packages. Explanation about 8255 with block diagram hope you understand. The 8255a is a programmable peripheral interface ppi device designed for use in intel microcomputer systems.
The intel 8255 or i8255 programmable peripheral interface ppi chip was developed and. The data bus buffer allows the 8085 to send control words to the 8259a and read a status word from the 8259 block diagram. Intel, interface consists of six 8bit io ports implemented with two intel 8255 program mable peripheral. The 82c55a is available in 40pin dip and 44pin plastic leaded chip carrier plcc packages. These include data transmission errors and control signals such as syndet, txempty. Mode 1 strobed inputoutput mode 2 strobed bidirectional bus io the functional configuration of the d8255 is programmed by the system software, so that normally no external logic is needed to interface peripheral devices or structures.
It consists of three 8bit bidirectional io ports i. Architecture, pin diagram, operational modes and control word format. Programmable interrupt controller pic 8259 is a programmable interrupt controller. Peripheral interfis a peripheral chip originallace chip y developed for the intel 8085 mcroproi cessor, and as such is a member of a large array of such chips, known as the mcs85 family. The 8259a is fully upward compatible with the intel 8259. There are 24 io pins which may be individually programmed in 2 groups of 12 and used in 3 major modes of. It has 3 independent counters, each capable of handling clock inputs up to 10 mhz and size of each counter is 16 bit. Programmable peripheral interface the 8255a is a general purpose programmable io device designed for use with intel microprocessors.
We can program it according to the given condition. The intel 82c55a is a general purpose programmable io device which may be used with many different microprocessors. Intel 8255a pin description let us first take a look at the pin diagram of intel 8255a. The functional configuration of each port is programmed by the systems software. The intel 8253 and 8254 are programmable interval timers pits, which perform timing and counting functions using three 16bit counters. The chip is fabricated using intel s high performance hmos technology. The 8255 provides 24 parallel inputoutput lines with a variety of programmable operating modes. The 825x family was primarily designed for the intel 8080 8085 processors, but later used in x86 compatible systems.
This specification, the intel 825 5x 10100 mbps ethernet controller family. Input or output instructions executed by the cpu either read data from, or write data into the buffer. These input signals work with rd, wr, and one of the control signal. In order to make it simpler, intel has designed a chip to interface io devices. A highlevel block diagram for the expansion board is drawn in two parts for better readability. Now let us discuss the functional description of the pins in 8255a.
The 8255 is contained in a 40pin package, whose pin out is shown below. Ppi 8255 is a general purpose programmable io device designed to interface the cpu. It consists of three 8bit bidirectional io ports 24io lines that can be configured to meet different system io needs. In essence, the cpu outputs a control word to the 82c55a. It found wide applicability in digital processing systems and was later cloned. Following is the table showing their various signals with their result. Datasheet the 82c55a is a high performance cmos version of the. Let us first take a look at the pin diagram of intel 8255a 8255a pin diagram. The 82c55a is fabricated on intel s advanced chmos iii technology which provides low power consumption with performance equal to or greater than the equivalent nmos product. The current address register holds a 16bit memory address used for the dma transfer each channel has its own current address register for this purpose. The cpu can read the complete status of the usart at any time.
The 8255 is a member of the mcs85 family of chips, designed by intel. It consists of data bus buffer, control logic and group a and group b controls. Programmable interrupt controller pic intel 8259 2. The 8255 has 24 io pins divided into 3 groups of 8 pins each. Input or output instructions executed by the cpu either read data. Group a and group b controls the functional configuration of each port is programmed by the systems software. The 8255a is a general purpose programmable io device designed to transfer the data from io to interrupt io under certain conditions as required. The intel 8255 or i8255 programmable peripheral interface ppi chip was developed and manufactured by intel in the first half of the 1970s for the intel 8080 microprocessor. When the signal is low, the microprocessor reads the data from the selected io port of the 8255. Block diagram of 8255 ppi read write control logic data bus. Programmable peripheral interface 8255 geeksforgeeks.
This threestate bidirectional 8bit buffer is used to interface the 8255. Software originally written for the 8259 will operate the 8259a in all 8259 equivalent modes mcs8085, nonbuffered, edge triggered. A high on this input clears the control register and all ports a, b, c are set to the input mode. A low on this input pin enables the communication between the 8255a, and the. It is a general purpose, multitiming element that can be treated as an array of io ports in the system software. Ppi 8255 is a general purpose programmable io device designed to interface the cpu with its outside world such as adc, dac, keyboard etc. This tristate bidirectional buffer is used to interface the internal data bus of 8255 pin diagram to the system data bus.
The d8255 is a programmable io device designed to be used with all intel cpus. The intel 8255a is a general purpose programmable io device which is designed for use with all intel and most other microprocessors. It consists of three 8bit bidirectional io ports 24io lines which can be configured as per the requirement. The 8254 solves one of the most common problems in any microcomputer system, the generation of accurate time delays under.
The 8254 is an advanced version of 8253 which did not offered the feature of read back command. The intel 8255a is a general purpose programmable io. The 8254 is a programmable interval timercounter designed for use with intel microcomputer systems. Programmable peripheral interface intel 8255 youtube. This tristate bidirectional buffer is used to interface the internal data lilts of 8255. It provides 24 io pins which may be individually programmed in 2 groups of 12 and used in 3 major modes of operation. The intel s 8255 is designed for use with intel s 8bit, 16bit and higher capability microprocessors. Mode 1 strobed inputoutput mode 2 strobed bidirectional bus io the functional configuration of the d8255 is programmed by the system software, so that normally no external logic is needed to. A block diagram of the sbc 8010 is shown in figure 1.