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 Post subject: ADC with 68000
PostPosted: Sun May 13, 2012 2:02 pm 
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Joined: Tue May 01, 2012 2:10 pm
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Location: nkana
I am newbie to 68000 programming. I need ideas on how to interface the 68000 to an ADC for analog to digital conversion. The 8 signals will have to be multiplexed and then connect to ADC TDA8703. example code is welcome


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PostPosted: Sun May 13, 2012 2:35 pm 
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Joined: Mon Dec 27, 2004 11:40 pm
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A good start would be The Art Of Electronics, Horowitz and Hill, ISBN 0 521 37095 7, chapters 9 and 11.


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PostPosted: Thu May 17, 2012 9:33 am 
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I read through the chapters you recommended. I have decided to use the 4051 analog mux to multiplex inputs to the ADC. I have a dilema on the ADC selection. I have the TDA8703 and AD574. I dont know wich one will be compatible with the 68000. The 8703 has a sampling rate of 40MHz, how will this affect my system since I am just converting analog voltages to digital?


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PostPosted: Fri May 18, 2012 10:51 pm 
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A quick look seems to say either will work. The TDA8703 is a little more involved on the digital side, the AD574 is a little more involved on the analogue side.

The AD574 is considerable slower than the TDA8703 but is 12 bit instead of only 8.


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PostPosted: Mon May 21, 2012 6:08 pm 
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Location: nkana
I had some luck and found ZN448 ADCs. My problems are far from over. I have the two ADCS that I need to hook the 8255 PPI and LCD and also a DAC. The 8255 has three ports and the ADCs will take up 22 pins. How do I connect the rest of the components?


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PostPosted: Sat Jun 09, 2012 5:45 am 
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I seem to be getting somewhere with the hardware. Now I am stuck with software. I would like to initialise the 8255 PPI and read an analog to digital converter.

I need code to set the 8255 in BSR mode because I want to use port c as control and connect ADCs and DACs to A and B.

Port A is at address 00046000
Port B is at address 00046002
Port c is at address 00046004


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 Post subject:
PostPosted: Sat Jun 09, 2012 10:56 pm 
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Joined: Mon Dec 27, 2004 11:40 pm
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Bit Set/Reset isn't so much a mode as an operation that can be used to set or clear individual bits of port C when using I/O mode 1 or mode 2.

This is done by writing the bit number and required state to the control register.

Look for bit set/reset format in any 8255 datasheet.


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 Post subject:
PostPosted: Sun Jun 10, 2012 12:17 pm 
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Joined: Tue May 01, 2012 2:10 pm
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Location: nkana
Elaborate what you mean by "isn't such a mode". Intend to operate ports A and B in mode 0 for ADC interface.


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