WHY DO WE USE RST INST. IN KITS/8085 MP BOARDS? WHY DONT WE USE HLT .?

Question

WHY DO WE USE RST INST. IN KITS/8085 MP BOARDS? WHY DONT WE USE HLT .?

why 8085 microprocessor has only 246 instructions rather than 256?

TRAP has got the highest priority interrupt. right?? under what condition the TRAP won’t be executed even when it is called??

Answer 1

Halt simply stops the processor from executing more program commands.  Reset (RST) does not stop execution, it only transfers it to a vector location (where is keeps on going).

Executing a Halt will still require Reset for the processor to continue operation.

There are only 246 instructions because that's what the designers of the IC at Intel wanted.

Trap will not execute if a Halt instruction is placed at memory address 024H, or if one of the other RST x.5 inputs has started to execute and the stack is being filled with PC information, or if the a stack overflow is clobbering the main memory and a Trap is vectored to a clobbered location.

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