What is interrupt acknowledge?

Interrupt acknowledge is the process of acknowledging a hardware interrupt, obtaining an interrupt vector address, and initiating the interrupt service routine in software. The INTA- (Interrupt Acknowledge) pin has the same timing as RD-, and external hardware is expected to provide an opcode in response to it. In the case of TRAP, RST7.5, RST6.5, and RST5.5, there is no specific interrupt acknowledge cycle like there is for INTR, but everything else is the same.