Difference between revisions of "Shift left"

Revision as of 16:31, 5 May 2011

Syntax

Syntax: shift_left register1, register2

• register1 = Register to shift left
• register2 = Shift left by value of register2

Use

Used to execute a logical bitwise operation shift left. Use shift_right to shift right.
In the example below we'll use R1 to store a 7Bit value 100 decimal (127 decimal value maximum) and 2 seperate flags set true.

1100100 = 100 Decimal
1 = Flag 1 true
1 = Flag 2 true
Value to store 00000000000000000000000110010011 (403 decimal, 193 hex)

Example

100:     leti R1, 00000193 //Set R1 to 403 (00000000000000000000000110010011 in binary)
         let R2, R1 //This will be used for 7bit value
         leti R5, 00000002 //This will be used to store the SHIFT amount
         andi R2, 000001FC //Perform bitwise AND operation on R2 using 508 (00000000000000000000000111111100 binary). R2 now equals 400 (00000000000000000000000110010000)
         shift_right R2, R5 //Perform bitwise SHIFT RIGHT on R2. Value changed from 400 (00000000000000000000000110010000) to 100 (00000000000000000000000001100100)
         let R3, R1 //This will be used to store the first flag
         andi R3, 00000001 //Perform bitwise AND operation on R2 using 00000000000000000000000000000001 binary. R2 now equals 1
         let R4, R1 //This will be used to store the second flag
         leti R5, 00000001 //This will be used to store the SHIFT amount
         andi R4, 00000002 //Perform bitwise AND operation on R4 using 00000000000000000000000000000010 binary. R2 now equals 2
         shift_right R4, R5 //Perform bitwise SHIFT RIGHT on R4. Value changed from 2 (00000000000000000000000000000010) to 1 (00000000000000000000000000000001)
         ret 

R2 Now equals 100, R3 equals 1 (true), R4 equals 1 (true). Now to change the values and store them back in R1.

Also see

List of OP Codes used in example.