Djnz instruction in 8051 meaning

The 8051 instruction set can be divided into 5 subgroups: - • Data Transfer - MOV instructions used to transfer data internal and external to the 8051 • The DJNZ instruction takes 2 machine cycles to execute (24 clocks) • If the 8051 is operating from a 12MHz crystal, the loop execution time is (10 * 24)/12000000 = 20usec The looping operation is used for running the same set of subroutine inside a program number of times as per the requirement. Consider the instruction DJNZ register; label is used for performing a loop operation. In this instruction, the register is decremented by 1; if this is not zero, then 8051 jumps to the target address referred by the label. Basic 8051 tutorial 1 2014-04-14. The 8051 micro has been on the scene for a number of years now since the early 80's. There are literally hundreds of derivatives.. Ti, Silicon, Atmel, Microchip, Cypress and many many more have come up with several products using this core.. I used Phillips personally. DJNZ decrements the location indicated by 1, and branches to the address indicated by the second operand if the resulting value is not zero. Execution steps: (PC) <- (PC) + instructionSize 1 Answer. Sorted by: 1. It's a special label indicating the current line. SJMP $ is equivalent to. currentline: SJMP currentline. And CJNE A,#'A',$+5 will jump to the instruction 5 bytes ahead when the condition matches. Embedded Systems Design with 8051 Microcontrollers: Hardware and Software. Steps of Mode 2 (3/3) 6. When TL0 rolls over from FFH to 00, the 8051 set TF0=1. Also, TL0 is reloaded automatically with the value kept by the TH0. - TL0= FCH, FDH, FEH, FFH, FCH(Now TF0=1) - The 8051 auto reload TL0=TH0=FCH. - Go to Step 6 (i.e., TL0 is incrementing continuously). Note that we must clear TF0 when TL0 rolls over.Thus, we can monitor TF0 in next process. Instruction. CJNE dest-byte,src-byte, rel. Function. Compare and Jump if Not Equal. Description. CJNE compares the magnitudes of the first two operands and branches if their values are not equal. The branch destination is computed by adding the signed relative-displacement in the last instruction byte to the PC, after incrementing the PC to the The 8051 microcontroller consists of RAM and ROM memories to store instructions. A Register is the main part in the processors and microcontrollers which is contained in the memory that provides a faster way of collecting and storing the data. The 8051 assembly language programming is based on the memory registers. The CJNE instruction compares the first two operands and branches to the specified destination if their values are not equal. If the values are the same, execution continues with the next instruction. See Also: DJNZ CJNE @Rn, #immediate, offset C AC F0 RS1 RS0 OV P Bytes 3 Cycles 2 Encoding 1011011n immediate offset Operation CJNE PC = PC + 3 IF (Rn) <> immedate PC = PC + offset IF (Rn