Parul Polytechnic Institute Subject Code : Name Of Subject : Microprocessor and assembly language programming Name of Unit : Introduction to Microprossor Topic : Pin function of 8085 Name of Faculty : H.M.Avaiya & Bhargav Halari

PIN FUNCTION OF 8085 Sub:malp Topic:pin diagram of 8085

PIN DIAGRAM OF 8085

8085 PIN FUNCTION :  A15-A8:  They represent upper half of the address bus of 8085 microprocessor and carriers upper byte of 16-bit address.  AD7-AD0:  They represent multiplexed address/data bus.  When ALE is high, they are used as lower half of the address bus and carriers lower byte of 16-bit address.  When ALE is low, they are used as 8-bit data bus to transfer data to and from microprocessor. SUB:MALP TOPIC:PIN DIAGRAM OF 8085

 ALE: It stands for Address latch enable. It is used to demultiplex multiplexed address/data bus(AD7-AD0). When it is high, AD7-AD0 carries lower byte of an address. When it is low,AD7-AD0 carries 8-bit data. ALE goes high in start of every machine cycle and stays high during first T-state. At the end of T1,it goes low. SUB:MALP TOPIC:PIN DIAGRAM OF8085

 IO/M: It stands input-output/memory. It differentiates between I/O and memory operation. When it is high, 8085 performs I/O operation (either read or write) and when it is low,8085 perform memory operation (either read or write)  RD,WR: The control signals RD and WR are used to perform the read and write operations respectively. When RD is low,8085 is reading from memory or input device. When WR is low,80MEMR,MEMW,IOW and IOR.85 is writing to memory location or output device. These signals together with IO/M are used to generate control signals SUB:MALP TOPIC:PIN DIAGRAM OF 8085

 S1,S0: They are status signals and IO/M, S1 & S0 together represents different machine cycles 8085 can perform. For example, IO/M =0, S1=0 & SO=1 represents memory write cycle.  SID,SOD: SID stands for serial input data and SOD stands for serial output data. SID is used to read the bits serially, while SOD is used to send data serially bit by bit. They are used for serial communication between 8085 and serial device. SUB:MALP TOPIC:PIN DIAGRAM OF 8085

 HOLD,HLDA: These signals are used with DMA controller. DMA controller uses HOLD to send the request for granting the control of buses to microprocessor. HLDA (hold acknowledge) is used by microprocessor to acknowledge the granting of request.  READY: It is used to synchronize the operation with slower peripherals. When it is high, the device is ready to perform the read or write operation. SUB:MALP TOPIC:PIN DIAGRAM OF 8085

 RESET IN, RESET OUT : When RESET IN is low, microprocessor resets itself and initializes program counter to 0000h. RESET OUT is used to inform all other peripherals in a system that microprocessor is being reset.  TRAP: It is nonmaskable interrupt and used only in emergency like power failure. Once it occurs it can not be stopped by software or hardware means. SUB:MALP TOPIC:PIN DIAGRAM OF 8085

 RST 7.5, RST 6.5, RST 5.5: They are known as restart interrupts and are maskable. They are controlled by EI/DI instructions as well as RIM & SIM instructions.  INTR: It is general purpose interrupt and also maskable. It is enabled and disabled by E1 & D1 instructions. SUB:MALP TOPIC:PIN DIAGRAM OF 8085

 INTA: It is interrupt acknowledge pin and used by microprocessor to acknowledge the acceptance of an interrupt request by device.  X1,X2: 8085 contains in built clock generator and X1 & X2 are used to connect crystal for this internal clock generator. Using it, 8085 generate system clock. All the operations performed by 8085 are synchronized to this clock SUB:MALP TOPIC:PIN DIAGRAM OF 8085

 CLK OUT: It is used to provide the system clock to other devices in a system.  Vcc, Vss: They are power signals. Vcc is connected to +5 volt. Vss is connected to ground SUB:MALP TOPIC:PIN DIAGRAM OF 8085