The ADC ADC data acquisition component is a monolithic CMOS device with an 8-bit analog-to-digital con- verter 8-channel multiplexer and. ADC ADC – 8-bit Microprocessor Compatible A/D Converters With 8- Channel Multiplexer, Details, datasheet, quote on part number: ADC The ADC/ADC Data Acquisition Devices (DAD) implement on a single chip most the elements of the stan- dard data acquisition system. They contain.

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The source must remain stable while it is being sampled and should contain little noise. Bottom rail of Reference voltage.

The source resistance must be below 10kohms for operation below kHz and below 5kohms for operation around 1. If Vcc and ground are used as reference voltages, they should be isolated by decoupling with a 1 microF capacitor. In this implementation the OE datasbeet is pulsed high one clock cycle after the EOC signal goes high and remains high until the data is safely stored into the desired register in the FPGA.

All of the signals are explained below.

The signal goes low once a conversion is initiated by the start signal and remains low until a conversion is complete. It goes low when a conversion is started and high at the end of a conversion.

This is an address select line for the multiplexer. Control signal from FPGA. Signal from the ADC. The ADC stores the data in a tri-state output latch until the next conversion is started, but the data is only output when enabled.


The maximum clock frequency is affected by the source impedance of the analog inputs. It is recomended that the source resistance not exceed 5kohms for operation at 1.

A, B, and C. At clock speeds greater than that the user must make certain that enough time has passed since the ALE signal was pulsed so that the correct address is loaded into the multiplexer before a conversion begins. The voltage level that, when received as an input, will output “” to the FPGA.

ADC Technical Data

This means it must remain stable daatasheet up to 72 clock cycles. The OE signal should conform to the same range as all the other control signals. Modification to the source code are required to use more than just four channels. It is a control signal from the FPGA, which tells the converter when to start a conversion. On the rising edge of the pulse the internal registers are cleared and on the falling edge of the pulse the conversion is initiated.

It is the MSB of the select lines. Be sure to consult the manufactures data-sheets for other chips. The minimum pulse width is ns.

Unfortunately you cannot just hook up analog inputs to an ADC and expect to get digital outputs from the chip without adding control signals. It is a pulse of at least ns in width. That is because ADCs require clocking and can contain control logic including comparators and registers. The clock should conform to the same range darasheet all other control signals. Address Lines Because the chip has an 8 channel multiplexer there are three address select lines: All control signals should have a high voltage from Vcc – 1.


Source code The source code datashet of a few of files. Clock The clock signal is required to cycle through the comparator stages to do the conversion. The following control signals are used to control the conversion.

National Semiconductor

The other files are enabled register, a register, datashee a multiplexer. C is the most significant bit and A is the least. Like the ALE pulse the minimum pulse width is ns. The ALE should be pulsed for at least ns in order for the addresses to get loaded properly.

It can be tied to the Start line if the clock is operated under kHz. Up to 72 if the start signal is received in the middle of an 8 clock cycle period. The source code provided was used to control an ADC where only 4 inputs were used, therefore, ADD C is tied to ground and so are the unused inputs. This is a bit of the datahseet converted output.