The Intel 8085 Microprocessor commonly known as 8085 Microprocessor is an 8-bit microprocessor.
It was developed in 1976.
8085 microprocessor is a single NMOS device.
It operates at +5V DC supply.
It uses a set of 246 instructions to perform operations.
It has a 40 pins Dual Inline Package (DIP).
Its clock speed is about 3 MHz.
It has 4 vectored interrupts and one of them is non-maskable and the other three are maskable interrupts.
Before talking about the pins let us first discuss the different types of signals generated by the pins in the 8085 microprocessor.
These signals can be grouped as follows--:
Power Supply Signals
Address Bus Signals
Data Bus Signals
Serial I/O Port signals
Interrupts…show more content… Interrupts are signals generated by hardware or software devices to bring the attention of the processor to an event immediately. They interrupt the normal execution of the microprocessor.Whenever the microprocessor encounters an interrupt, it suspends its all ongoing processes (saves its state) to respond to that interrupt.It then starts processing the program indicated by the interrupt signal and after the complete execution of the new program the processor returns to its original state.
There are five kinds of hardware interrupts in 8085 microprocessor-:
In these the TRAP is the non- maskable interrupt and the other 4 are maskable interrupts.
Pin 6 (TRAP)
TRAP is an non-maskable interrupt and it has the highest priority.
It is both edge and level triggered.
It cannot be disabled.
TRAP signal must go from low to high and it should remain in the same high condition for a certain amount of time.
This signal is usually generated for power failure and for emergency shutoff.
Pin 7 (RST 7.5)
It is a maskable interrupt and has the second highest priority.
It can be triggered by the positive edge…show more content… This interrupt can be enabled by EI instructions and can be disabled by DI instructions.
This pin needs to be held in high condition for a specific period of time.
Pin 9 (RST 5.5)
It is a maskable interrupt and has the fourth highest priority.
Like the RST 6.5 it is also level triggered only.
And also like the RST 6.5 it needs to be held in the high condition for a specific period of time.
Pin 10 (INTR)
It is a general purpose maskable interrupt and has the lowest priority.
Like the RST 6.5 and RST 5.5 it is also level triggered.
INTR can be used to vector microprocessor to any specific subroutine having any address at any time.
Pin 11 (INTA)
This pin indicates whether the INTR request was acknowledged by the microprocessor or not. INTA stands for Interrupt Acknowledge.
INTA is an active out going low signal.
If this pin gives a low output then this means that INTR’s request has been acknowledged by the microprocessor.
Pin 3 and Pin 36
Reset Out and Reset In pins
Reset In –This pin is used to reset the microprocessor.
It is an active low signal.
If a low signal pertains on this for at least 3 clock cycles then the microprocessor resets