Hello guys, Let’s see how to generate a lookup table for even numbers.
There are three addressing modes in 8051 micro-controller: Immediate addressing mode, Direct addressing mode and indirect addressing mode. We use indirect addressing mode in this program to generate a lookup table for even numbers.
Note: When we do division operation in 8051 accumulator register A holds quotient and accumulator register B holds the reminder.
- Initialize a register with the base address of memory location where lookup table needs to generated
- Initialize counter register with the number of elements in lookup table
- Initialize natural number register (Rd) with 01h
- Move 02h to accumulator register B
- Move value in Rd to accumulator register A
- Divide A by B and check if the value in B is 0
- If the value in B is 0 then store the value in Rd to the memory location, increment Rd and address register and jump to step 5
- Else increment Rd and jump to step 5
- Repeat steps 5-7 until counter register becomes zero
Here is example code for a lookup table of first 10 even numbers stored in the internal memory location with starting address 0xA0
LJMP main ; Long jump main label
MOV R0,#0a0h ; Initializing base address of memory location
MOV R1,#0ah ; Initializing counter register
MOV R2,#01h ; Initializing first natural number
loop: MOV B,#02h
DIV AB ; A/B here register A holds quotient and B holds reminder after this instruction is executed
CJNE R3,#01h,store ; Checking number is whether odd or even
store: MOV A,R2 ; Store the number if it is even
MOV @ R0,A ; Moving odd number value to memory location
INC R0 ; Incrementing address register