The Shift and Rotate instructions include: SHL - Shift Left. ROL – Rotate Left. SHR - Shift Right. ROR – Rotate Right. SAL – Shift Arithmetic Left. RCL
shift all bits left the bit that goes off is set to CF and the same bit is inserted to the right-most position. Example: MOV AL
When arithmetic instructions executed contents of the flag register change. ROL. Rotate left. ROR. Rotate right. RCL. Rotate left through carry. RCR.
http://site.iugaza.edu.ps/ahaniya/files/Assembly-Language-Lab9.pdf
In the RCL instruction the contents of the destination operand undergoes For 8086 microprocessor
RCL and RCR Instructions. • SHLD/SHRD Instructions The SHL (shift left) instruction performs a logical left ... ROL (rotate) shifts each bit to the left.
RCL. Rotate. Left through. Carry. RCL DCount Same as ROL except carry is Conditional Jump instructions in 8086 are just 2 bytes long. 1-byte.
The other two rotate instructions RCL and RCR
The 8086 can perform two types of Shift operations; the logical shift and the arithmetic There are four rotate operations (ROL ROR
Assignment no:4 on chapter no :3 : Instruction set of 8086. 1) Describe any two string operation instruction of 8086 with syntax & one (i) ROL vs RCL.
80x86 Instruction Reference Instructions are listed in this reference in this general order Instructions that are available in the 32-bit machines only are listed in lowercase ! DATA MANIPULATION INSTRUCTIONS - Moving Data: MOV PUSH PUSHA POP POPA pushad popad XCHG - I/O: IN OUT INS OUTS - Address Loading: LEA LDS/LES/lfs/lgs/lss
MUL instruction • The MUL (unsigned multiply) instruction multiplies an 8- 16- or 32-bit operand by either AL AX or EAX • The instruction formats are: MUL r/m8 MUL r/m16 MUL r/m32 Implied operands: 26 MUL examples 100h * 2000h using 16-bit operands: data val1 WORD 2000h val2 WORD 100h code mov axval1 mul val2 ; DX:AX=00200000h CF=1
80386 introduced 32-bit mode and paging Supported modern OSes like Unix and Windows NT 80486 was almost the same ISA but faster Cache pipelining What would have been the 80586 was sold as the“Pentium” The x86 ISA: CISC vs RISC Called CISC because it predates the 80s/90s RISCrevolution Pre-RISC ISAs were for human assembly programmers
The 80x86 Instruction Set Page 245 The trace ?ag enables or disables the 80x86 trace mode Debuggers (such as CodeView) use this bit to enable or disable the single step/trace operation When set the CPU inter-rupts each instruction and passes control to the debugger software allowing the debugger to single step through the application
There are 4 types (ROL ROR RCL RCR) of Rotate instructions ROL = Rotate LEFT This instruction rotates all the bits in a specified word or byte to the left some number of bit positions The data bit rotated out of MSB is circled back into the LSB It is also copied into CF In the case of multiple-bit rotate CF will contain a
ROL Instruction The ROL (rotate left) instruction shifts each bit to the left The highest bit is copied into the Carry flag and the lowest bit position No bits are lost Example: mov al11110000b rol al1 ;AL = 11100001b CF = 1 Application: Exchanging Groups of Bits