16 bit Assembly

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TEST   - Logical Comparison Instruction

The TEST instruction AND's the operands, and discards the result. The effect of the AND operation sets the Parifty PF), Sign (SF) and Zero (ZF) flags.

This command has 3 parts, Instruction, Register or memory address, then either a Register, Immediate value or a memory address.

Assembly Sample Description   16 bit Machine Code
TEST AL, 0x30;  8 bit immediate to AL Register   A8 30
TEST CL, 0x30;  8 bit immediate to 8 bit Register   F6 C1 30
TEST AX, 0x3030;  16 bit immediate to AX Register   A9 30 30
TEST CX, 0x3030;  16 bit immediate to a Register  F7 C1 30 30
TEST [BX], 0x3030;  16 bit immediate to memory address   F7 47 30 30
TEST [BX+2], 0x3030;  16 bit immediate to memory address
  with offset 		  F7 47 02 30 30
TEST [BX], AX;  16 bit Register to memory address   85 47
TEST [BX+2], AX ;  16 bit Register to memory address
  with offset 		  85 47 02
TEST AX, CX;  16 bit Register to a Register  85 C1



Last Update 13/02/2023