Clock Pulse from 8051

there are two or three ways to complete.

use timer 1 or 2,

use registor like B or any Rx rigestors to impletement sub one as a subroutine is another good way .

for example, 12M hz means a instructor takes a millisecond. so that you can set B or Rx as 100ms or 250ms;

binary is 44h or 0fah;

and A sub one, while A set up 5 or 2 and use flag f0 as toggle(cpl). you can get what you need.

you can use any lead pins, of cause pi.1