Microprocessors and Microcontrollers by Pearson

THE 8051 MICROCONTROLLER 12.47

DJNZ R3,OUTER

SDJNZ R2,OUT_MOS

RET

END

0.5 secs.

1.5 secs.

Figure 12.26 | Square wave generated at all pins of Port 1

We might need three registers to get a large delay of 0.5 secs. For the inner loops, let us use reg-

isters with the maximum count of 255. For the outer most loop,let the register be loaded with

the number N, which we calculate as follows.

0.5 × 1000 × 1000 μsecs = N × 255 × 255 × 2 × 1.085 μsecs

500 × 1000 = 141104 N

N = 3.5 = 4 (approx)

 is will give a delay of 0.5 secs.

We call the procedure which gives a delay of 0.5 secs, as DELAY_HALF.  is is just a label

for the procedure, and indicates the ...