It has to be calculated, you can not generate the control word it's an hex value for controlling the ports of 8255A
I have made a project which interfaces seven segment waiting display with 8086 and 8255. If there is anyone in need of this project I can help. Write me on this page and I will write the detailed explanations.
E.g. 8085, 8086, 8255, 8051, 6800, 8257, 8251 and many more...
first connect the 8255 to the 8086 microprocessor and configure it using the CWR then connect the key board to the 8255
It means an 8 bit parallel I/O interface, as opposed to 8251 which is a serial I/O.
Neither the 8155 nor the 8255 are considered to be microprocessors. The 8155 is an integrated RAM, IO, and Timer device designed for the 8085. The 8255 is an Programmable IO controller.
In order to interface more than 64K of memory using the 085, you would need an external address register, perhaps maintained by the 8255, which contained an offset register for part of the memory address space. This would be similar to how the 8086/8088 processors implemented expanded memory before using the 80386 and above processors.
The 8051 can directly interface with a number of I/O. The 8255 just gives you the abilty to access 3 eight bit ports using a minimum number of control bits from the 8051
8255 is a programmable peripheral device, a chip used to control peripheral devices connected to/with in a computer in the 8086 based machines. It's a general purpose i/o controller, produced by Intel. More details: http://www.electronics.dit.ie/staff/tscarff/8255PPI/8255.htm http://www.wantronix.de/pdf/decision/8255pci.pdf
As port A is used as an output port, control word for 8255 is 80H.Stepper Motor Control Program:6000H Excite code DB 03H, 06H,09H, OCH : This is the code sequence for clockwise rotationSubroutine to rotate a stepper motor clockwise by 360° - Set the counts:MVI C, 32H : Set repetition count to 50ıοSTART: MVI B, 04H : Counts excitation sequenceLXI H, 6000H : Initialize pointerBACK1: MOV A, M : Get the Excite codeOUT PORTA : Send Excite codeCALL DELAY : WaitINX H : Increment pointerDCR B : Repeat 4 timesJNZ BACK lDelay Subroutine:Delay: LXI D, CountBack: DCX DMOV A, DORA EJNZ BackRET
the different operating modes of 8255 are as follows 1)bsr mode 2)i/o mode -bsr mode can only program using port c and is used when d7=0 in control word -i/o mode can be used for all ports a,b,c(upp),c(low) respectively and is used when d7=1
For displaying data on output in 8085 ,we use 8255 programmable peripheral interface.its an 40 pin i.c. Other micro processors use their suitable and pre designed interfacing devices............................
it's 00000111 binary = 07 H