There are five interrupt signals in 8085 microprocessor. These signals are used to inter rut the current program under execution and transfer the execution to a predefined interrupt service routine (ISR) stored at location reserved for the corresponding interrupt signal. These interrupt signals have a predefined priority. If more than one interrupt signals goes high simultaneously the interrupt has higher priority will be given first response. Followings are various interrupts defined priority wise.
TRAP it is a no maskable interrupt which cannot be disabled and has highest priority.
RST 7.5 RST 6.5 RST 5.5 These are maskable vectored interrupt called restart interrupts. Priority order of these interrupts is RST 7.5 RST 6.5 and then RST 5.5 .
INIR called interrupt request it is a general purpose non vectored interrupt. It has lowest priority among all above interrupts. It requires an external hardware to transfer the execution to one of the eight possible locations.
Other than these input interrupt signals one more signal is related to interrupts defined below.
INTA it is called interrupt acknowledge signal. It is an active low output signals. In goes low when microprocessor receives high INIR signals.
All these interrupts will discussed in detail in chapter 8.