Intel 80287 Flag Operation with the Basic Instruction SET, Status Flags, Control Flags, Hm====i

BASIC INSTRUCTION SET

HIGH ADDRESS ..

hm====i

OPERANDS FROM ~n\\\\\\n\\l\~\\\\\\\

PREVIOUS PUSH

INSTRUCTIONS ~\\\\\\\\\\\\\\\\\\\\\\\\

SP _ OPERAND

SS

LOW ADDRESS	Ok	,
	BEFORE	AFTER
	POP OPERAND	POP OPERAND

POP copies the contents of the slsck location before SP to the operand In the Instruction. POP then Increments SP by 2 bytes (1 word).

G3010e

Figure 3-3.POP

3.2 FLAG OPERATION WITH THE BASIC INSTRUCTION SET

3.2.1 Status Flags

The status flags of the FLAGS register reflect conditions that result from a previous instruction or instructions. The arithmetic instructions use OF, SF, ZF, AF, PF, and CF.

The SCAS (Scan String), CMPS (Compare String), and LOOP instructions use ZF to signal that their operations are complete. The base architecture includes instructions to set, clear, and complement CF before execution of an arithmetic instruction. See figure 3-5 and tables 3-1 and 3-2.

3.2.2 Control Flags

The control flags of the FLAGS register determine processor operations for string instructions, maska- ble interrupts, and debugging.

3-4