Problems of digital clock by 8051...

mikemike said:

Hi everyone, i'm new in here.
i'm now doing a digital clock by using 8051 without using a rtc clock chip.
i've done it by a 16bit mode timer, but after i show to my tutor, he said a 16bit timer can't be so accurate, and it's quite obvious after days running. He suggests me to use 8bit with auto reload instead.
So, how to do it with a 8bit ones???

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Nigel Goodwin said:

Can't help you on 8051's, but I fail to see why an 8 bit timer would be any more accurate than a 16 bit one?. The accuracy of your clock should be dependent upon the accuracy of it's clock source, and how well you program it.

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mikemike said:

My tutor explain to me, according to his experiences, the 16bit requires some :mu: s to count over, but the 8bit is count over using hardware(inside 8051). Therefore, it's more accurate than the 16bit one.

forgive me for my english.
anyway,thank you for your reply.

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TMOD = 0X25;  //counter 0 in mode 1 (16 bit counter)  , timer 1 in mode 2 (auto reload from TH1
TH1 = 100; //start timer 1 from 100, it will count 156 steps 
ET1 = 1; //enable timer 1 interrrupt (if you need to, and that's obvious in your application)
TR1 = 1; //Enable Timer/counter 1 to count

ikalogic said:

Well.. i my point of view, what makes the 8-bit counter more reliable, is that the "autorelaoding" is done automatially, always at the same time, but when using a 16 bit timer (in 8051), you have to reload it manually, after an interrupt is exected, or by pooling, making it more difficult to control the timing and acheive precision.

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Nigel Goodwin said:

So basically it's a limitation of the poor hardware?.

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