80C186EB/80C188EB Microprocessor User's Manual - CEUNES

INSTRUCTION SET DESCRIPTIONSTable C-4. Instruction Set (Continued)Name Description OperationFlagsAffectedINTNOTE:Interrupt:INT interrupt-typeActivates the interrupt procedurespecified by the interrupt-typeoperand. Decrements the stack pointerby two, pushes the flags onto thestack, and clears the trap (TF) andinterrupt-enable (IF) flags to disablesingle-step and maskable interrupts.The flags are stored in the format usedby the PUSHF instruction. SP isdecremented again by two, and the CSregister is pushed onto the stack.The address of the interrupt pointer iscalculated by multiplying interrupttypeby four; the second word of theinterrupt pointer replaces CS. SPagain is decremented by two, and IP ispushed onto the stack and is replacedby the first word of the interrupt pointer.If interrupt-type = 3, the assemblergenerates a short (1 byte) form of theinstruction, known as the breakpointinterrupt.Instruction Operands:INT immed8(SP) ← (SP) – 2((SP) + 1:(SP)) ← FLAGS(IF) ← 0(TF) ← 0(SP) ← (SP) – 2((SP) + 1:(SP)) ← (CS)(CS) ← (interrupt-type × 4 + 2)(SP) ← (SP) – 2((SP) + 1:(SP)) ← (IP)(IP) ← (interrupt-type × 4)The three symbols used in the Flags Affected column are defined as follows:– the contents of the flag remain unchanged after the instruction is executed? the contents of the flag is undefined after the instruction is executedüthe flag is updated after the instruction is executedAF –CF –DF –IF üOF –PF –SF –TF üZF –C-19