Diamond Systems 16-Channel 12-Bit Analog Output PC/104 Module LSB = 1/2048 x Full-Scale Voltage

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Offset Binary Coding (for bipolar output ranges)

This method takes into account the fact that the lowest output voltage is not zero but a negative value. The output voltage is given by:

Output Voltage = (Output Code / 2048) x Full-Scale Voltage - Full-Scale Voltage

Example:

Output code = 1024, full-scale voltage = 5V

 

Output voltage = (1024 / 2048) x 5 - 5 = (0.5 x 5) - 5 = -2.500V

Note the difference between this output voltage to the output voltage using straight binary coding shown above using the same output code.

Conversely, the output code for a desired output voltage is given by:

Output Code = (Desired Output Voltage / Full-Scale Voltage) x 2048 + 2048

Example:

Desired output voltage = 0.485V, Full-scale voltage = 2.5V

 

Output Code = (0.485 / 2.5) x 2048 + 2048 = 0.194 x 2048 + 2048 = 2445

 

(rounded down)

The relationship between D/A resolution and Full-scale voltage is:

1 LSB = 1/2048 x Full-Scale Voltage

Example: Full-scale voltage = 5V; 1 LSB = 5V / 2048 = 2.44mV

The reason that 1 LSB for a bipolar range is twice the magnitude of 1 LSB for a unipolar range with the same full-scale voltage is that for the bipolar range, the full voltage span is twice the magnitude. For example, a unipolar range with a full-scale voltage of 5V has a range of 0V to 5V, for a total span of 5V. However, a bipolar range with a full-scale voltage of 5V has a range of ±5V, for a total span of 10V. Here is a brief overview of the relationship between output code and output voltage:

Output Code

Explanation

Output Voltage for ±5V Range

0

Negative full scale

-5V

1

Negative full scale + 1 LSB

-4.9976V

2047

-1 LSB

-.0024V (-2.44mV)

2048

0V

0V

2049

+1 LSB

+.0024V (+2.44mV)

4095

Positive full scale - 1 LSB

+4.9976V

⇒Note: Again, an output code of 4096 would be required to generate the positive-full-scale output voltage, but since that is impossible, the maximum output voltage is 1 LSB less then positive full scale.

Copyright 2001 Diamond Systems Corp.

Ruby-MM-1612 User Manual V1.1 P. 15

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Contents
RUBY-MM-1612 Table of Contents Description O Header Pinout Signal Name DefinitionBoard Configuration Base Address Configuration Header J5 Position Hex DecimalBase Address Full-Scale Voltage Analog Output Range ConfigurationAdjustable Reference Voltage On-Board Reference Full-Scale Voltage SelectionAnalog Output Configuration Header J4 Range RUBY-MM-1612 Board Drawing Reset information Ruby-MM-1612 I/O MapBase + Write Function Read Function Base + 1, Write DAC MSB register Base + 0 or 1, Read Update DACsRegister Definitions Base + 0, Write DAC LSB registerBase + 3, Write External trigger register Definitions Configuration Register82C55 Digital I/O Chip Operation 82C55 Register MapAnalog Output Ranges and Resolution Full Scale 1LSBFull Scale 10. D/A Code Computation Offset Binary Coding for bipolar output ranges LSB = 1/2048 x Full-Scale VoltageOutput Code Explanation Output Voltage for ±5V Range HOW to Generate AN Analog Output Hardware Update CommandTo generate an analog output on one or more channels Two channel output Examples Single channel outputCalibration Procedure Miscellaneous SpecificationsPinouts FeaturesOrdering Information Description82C55A Pin Description Functional DiagramGroup a and Group B Controls 82C55A Functional DescriptionData Bus Buffer Read/Write and Control LogicPorts A, B, and C Mode Selection82C55A Operational DescriptionInte Flip-Flop Definition Single Bit Set/Reset Feature FigureOperating Modes Interrupt Control FunctionsMode 0 Basic Input Mode 0 Basic OutputMode 0 Configurations Control Word #4 Control Word #8 Input Control Signal Definition STB Strobe InputIBF Input Buffer Full F/F Intr Interrupt Request Output Control Signal DefinitionInput Operations Mode 2 Strobed Bi-Directional Bus I/OBi-Directional Bus I/O Control Signal Definition Output OperationsMode Control Word Mode 2 Combinations Current Drive Capability Special Mode Combination ConsiderationsReading Port C Status Figures 15 Applications of the 82C55A