Hi Forum Members,

I am in the process of designing a digital oscilloscope Here is how I am planning to do it...

Hardware Configuaration:

1. I will be using a 8 bit High speed 100MSPS ADC such as AD9283-100 which will take the applied analog signal and convert it to 8 bit digital value.

2. A CPLD such as XC9574 will sit inbetween the ADC and P89V51RD2. The CPLD will also be connected to a High speed SRAM 10ns.

3. A GLCD 128X64 will be connected to P89V51RD2.

4. A low speed multichannel 8 bit ADC such as PCF8591 will be connected directly to P89V51RD2 and it will be used for reading Rotary knobs on front panel.



Working

1. User can select desired Volts/Div, Sweep Time, Trigger etc through front panel controls. P89V51RD2 will read the slow 8 bit ADC ie. P8591 to read the status of these knobs.

2. The P89V51RD2 will send signal to CPLD to intiate sampling at appropriate sampling speed depending upon sweep speed selected.

3. CPLD will read the ADC at the desired speed and wait for the trigger value once that is reached ADC will start writing the read data into fast SRAM. 256 samples will be stored into the SRAM.

4. Once this reading and storing is done CPLD will signal P89V51RD2 to acknowledge the same.

5. P89V51RD2 in response will signal CPLD to send the stored data CPLD will read this data from fast SRAM and transmit it to micro. Micro will go on saving this data into its internal RAM.

6. Now the micro will either plot the waveform onto the GLCD or will transmit these values to PC through RS232 link a software in PC can then show the waveform on monitor.

7. While micro is displaying things on GLCD it will signal CPLD to start sampling again a fresh cycle and this will continue.

I want to know is this a feasible idea to implement ? Are there any pit falls ? Any precautions or things to be taken care of ? Any other suggestion you can tell from your experience ?

At present I am planning to use fast 10ns access time cypress FIFO memory availble from RS. Can you guys please suggest some other FAST SRAM better if RS stock number.

Thanks & Regards,
Prahlad Purohit