I haven't learnt about Parallel Load? What is it
hi.
On the 4510 are 4 pins marked L1,2,4,8.
When all set Low and pulsing Pload Hi, All the Q outputs will be Low.
If however you wanted preload the 4510's with say '29', the MSD L8,4,2,1 would be connected as Lo,Lo,Hi,Lo and the LSD as Hi,Lo,Lo,Hi.
So now when the Pload is pulsed hi, the 4510 and LED displays would show '29'.
You could then could count down from '29' to '00'
Pressing Pload would reload the 29, or whatever number you have set on the L8,4,2,1 pins.
OK.