Hi friends: I got a serious problem with 74LS123. 74LS123 has been configured as following: 1CLR-----VCC 1A-------GND 1CEXT----100PF( one pin is conected to GND ) 1REXT----120K 1B-------INPUT 1Q-------OUPUT Input keeps changing from 1V to 3.5V repeatedly. Why this chip can not be triggered? Beg for you help....
Your circuit description does not line up with the data sheet I have for the 74ls123 - The capacitor is connected between pins 14 and 15, the resistor between pin 16 and VCC (pin 16). Try this configuration and it might have a better chance of working. How do you mean the input is changing from 1v to 3.5v?? Why are you using a 74ls123 to generate a 100mS pulse? If you're using a micro, it is normally more than capable for generating pulses. Methinks a good read of the datasheet is in order. How does this hardware question relate to Keil's C compiler??? I suggest using a different forum.
Thank you for your generous helps... The input to pin 4 is a slowly rising since wave, what I want to do is to use 74LS123 as a interface between analogy input and MCU for producing impluse.
Sounds like you need a Schmitt Trigger, rather than a monostable? Anyhow, what has any of this got to do with Keil software tools...?
so sorry friends... I am using keil c51 to development my project and here is the only place which can appear in my mind right now... Thank you and have a good weekend...