Hello every one.

i would like to use ADC 0809 along with AT89c52 in its continuoues mode, but having a problem with ALE/OEC/SC/ 3addresses. as i,m going to use three inputs so here is my idea and any suggestion are welcome.
actually i have used all the ports in the microcontroller for different purposes.

i have three sensors in my project. that is why i have to change ALE pluse.

Usually the control signals EOC (end of conversion), SC (start conversion), ALE (address latch enable) and OE (output enable) are interfaced by means of a microprocessor or microcontroller. However, to operate ADC 0809 in its continuous mode without using any microcontroller, the input control signals ALE and OE, being active-high,can be tied to Vcc (+5 volts). The input control signal SC, being active-low, initiates start of conversion at falling edge of the pulse, whereas the output signal EOC becomes high after completion of digitisation. This EOC output is coupled to SC input, where falling edge of EOC output acts as SC input to direct the ADC to start the conversion.
As the conversion starts, EOC signal goes high. At next clock pulse EOC output again goes low, and hence SC is enabled to start the next conversion. Thus, it provides continuous 8-bit digital output corresponding to instantaneous value of analogue input. The maximum level of analogue input voltage should be appropriately scaled down below positive reference (+5V) level.
the three addresses can be tied to the gound to be active low.


by this way, i,m sure it can suport 1 input signal, but as far as i know to have more than one input the ALE should goes low and high not high at all.

so my question is that, is it possible to use an 555 timer to generate these signals along with inverter to generate approxmitally 469 KHz through 1n farad and 1k resistor. these can generate 469 Khz and its more than enough for ADC 0809.

i have the circuit with me but i dont know how to put it here :).

so any suggestion about this are welcome,
but one more question, if my idea is right so is there any limits of ALE signals, i mean the maximum clock signals.

Regards
Albarkani