About Dallas processor

Dear friends
i have a small doubt on Ds89c420 microcontroller
i.e
how can we find the values TH& Tl for this microcontroller and give some example using programming.please help me to clarfy this doubts.
And if anybody have mazidi book please the problem no:9-23 in the timers programm .please help me to solve this problem and give explanation for that problem.

i wait for your responses..

please give me reply me as soon as possible.

Hi,

Same as normal 8051 Family. if i remember correctly,the default clock source for timers is same as normal 8051 microcontroller (1/12 clock-12 clock per cycle),but you can change it to 1 clock per cycle by changing a SFR.

tq for ur rply.can u explain with a example plz

ngagearun said:

tq for ur rply.can u explain with a example plz

Click to expand...

Hi,
For Example : Let assume we have 1) AT89C51 2) DS89C420 , both with a 24MHz Clock

In AT89C51 , The Clock source for timers is same as machine cycle ,so it is 24MHz/12=2MHz

In DS89C420 ,when you program it and don't change anything in special SFRs, is same as AT89C51 (24MHz/12=2MHz, for compatibility) , but DS89C4xx series have some special SFR bits for timers :

1) TxM in CKCON Register and TxMH in CKMOD Register (for Ex : T0M & T0MH for timer 0 , .. etc). if you set TxM & Clear TxMH bit for a timer , the clock source for that timer will be System Clock/4. For Ex: if you set T0M=1 & T0MH=0 , the clock source for TIMER0 will be 24MHz/4=6MHz.
if you set TxMH bit for any timer (regardless of TxM state) the clock source will be same as system clock , for Example if you set T0MH=1 (T0M state doesn't Matter) , the clock source for Timer0 ,will be same as system clock=24MHz.

This is true for all 3 timers of DS89C4xx , but Timer2 is a different beast (with some interesting features). I strongly recommend that you read this Document Carefully :

Good Luck!

thanq very much.iam new to the emebdded system.right now iam referring the mazidi text book only.i want some additional programm.can u give some websites where i can get all that one and please help me in the nterview point view where should i get all this.

---------- Post added at 18:03 ---------- Previous post was at 18:01 ----------

please give me the programm to generate the triangle and sawtooth,ramp wave in embedded c

Hi,

The Mazidi text book is an excellent book for learning 8051 family. For more information (with project source codes) you can use these sites :
1) **broken link removed**

2) **broken link removed**

3) Projects - Free 8051 Microcontroller Projects

and use your c Compiler Manual.

Good Luck!