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RCL  -  Roll left with carry Instruction


The RCL instruction is used to rotate the bits to the left.

As each bit is rotated it passes in to the Carry flag, where it can be assessed using a conditional jump JC or JNC.

As each bit moves off the highest bit it is inserted in the lowest bit.

This command has 3 part the Instruction, a Register or memory address, and the number of bits to rotate left.


Assembly
Sample		 Description   16 bit Machine
  Code
RCL AL, 1;  Rotate AL left by 1 bit   D0 D0
RCL AL, CL;  Rotate AL left by value of CL   D2 D0
RCL AL, 0x03 ;  Rotate AL left by 8 bit immediate   C0 D0 03
RCL AX, 1;  Rotate AX left by 1 bit   D1 D0
RCL AX, CL ;  Rotate AX left by value of CL   D3 D0
RCL AX, 0x03 ;  Rotate AX left by 8 bit immediate   C1 D0 03
RCL [BX], 1;  Rotate memory address left by 1 bit   D0 17
RCL [BX], CL;  Rotate memory address left by value of CL   D2 17
RCL [BX], 0x03 ;  Rotate memory address left by 8 bit
;  immediate 		  C0 17 03
RCL [BX+2], 1;  Rotate memory address left by 1 bit   D0 57 02
RCL [BX+2], CL ;  Rotate memory address left by value of CL   D2 57 02
RCL [BX+2], 0x03 ;  Rotate memory address left by 8 bit
;  immediate 		  C0 57 02 03