Introductory Materials > Input and Output Data Buffer Architecture

Analog In Word

All instruments may write data to the input buffer from analog input signals or from the digital input port. Similarly, data contained in the output buffer may be written to the DAC or to the digital output port on DI-200 Series instruments; or to either DAC (DAC1 or DAC2) or to the digital output port on DI-400 Series, DI-500 Series, DI- 720, and DI-730 instruments (DI-401 and DI-700 instruments do not support output operations, therefore there is no output buffer). The following describes the format of any word appearing in the input or output buffer. These data word formats assume that only the SDK is running. If WINDAQ software is running in conjunction with the SDK, Y1 and Y0 are undefined. Because DI-200 Series instruments have only one I/O port, both DMA data and control information (i.e., commands, status, etc.) must share this single port. Therefore, in order to distinguish the word as DMA data (as opposed to control information), the two LSB's of the data word must be zero.

Analog In Word

All 12-bit instruments (DI-200, DI-400, DI-401, and DI-500 Series) with signal averaging off, or DI-220, DI- 221TC, and DI-222 always (regardless of signal averaging)

D=indicated digital I/O line; *If you are looking at the first channel in the scan list, Y1 reflects the inverted state of the remote start/stop flag and Y0 reflects the inverted state of the event marker flag. Otherwise, Y1 and Y0 are zero. If analog data is a unipolar signal, the number is a straight binary value. Bipolar signals are in 2's complement format.

All 12-bit instruments (DI-200, DI-400, DI-401, and DI-500 Series) with signal averaging on, or all 14-bit instruments (DI-210, DI-410, DI-700, DI-720 and DI-730)

D=indicated digital I/O line; *If you are looking at the first channel in the scan list, Y1 reflects the inverted state of the remote start/stop flag and Y0 reflects the inverted state of the event marker flag. Otherwise, Y1 and Y0 are zero. If analog data is a unipolar signal, the number is a straight binary value. Bipolar signals are in 2's complement format.

All 16-bit instruments (DI-700, DI-720, and DI-730)

D=indicated digital I/O line; If analog data is a unipolar signal, the number is a straight binary value. Bipolar signals are in 2's complement format.

Analog Out Word

All instruments that have analog output capability.

D=indicated digital I/O line; If analog data is a unipolar signal, the number is a straight binary value. Bipolar signals are in 2's complement format. R=reserved.

Digital In Word

All Instruments Supporting Digital In

D=indicated digital I/O line; X=ignore; *If you are looking at the first channel in the scan list, Y1 reflects the inverted state of the remote start/stop flag and Y0 reflects the inverted state of the event marker flag. Otherwise, Y1 and Y0 are zero.

Digital Out Word 

All Instruments supporting Digital Out

D=indicated digital I/O line; X=ignore.

A/D Coding

FS = full scale; *DI-221TC, DI-400 Series, DI-500 Series, DI-700, DI- 720, DI-730, and DI-5001 instruments do not support unipolar operation. **All data is left-justified, with extraneous bits (if any) equal to zero.

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