Principles of Operation
83
Data Format and Transfer
DT9857 and DT9857E modules use offset binary data encoding, where 000000 represents
negative full-scale, and FFFFFFh represents positive full-scale. Use software to specify the
data encoding as binary. The ADC outputs FFFFFFh for above-range signals, and 000000 for
below-range signals.
Before you begin acquiring data, you must allocate buffers to hold the data. A Buffer Done
event is returned whenever a buffer is filled. This allows you to move and/or process the data
as needed.
We recommend that you allocate a minimum of two buffers for continuous analog input
operations. Data is written to multiple allocated input buffers continuously; when no more
empty buffers are available, the operation stops. The data is gap-free.
Note:
DT9857 and DT9857E modules have a 16 kSample input FIFO that is used to store the
acquired data before it is sent to the host.
Error Conditions
DT9857 and DT9857E modules report any overrun errors by sending an overrun event to the
application program. This event indicates that data buffers are not being sent from the module
to the host fast enough, and the A/D converter ran out of buffers. To avoid this error, try one
or more of the following:
• Reduce the clock rate of the A/D
• Increase the size of the buffers
• Increase the number of buffers
• Close any other applications that are running
• Run the program on a faster computer
If one of these error conditions occurs, the module stops acquiring and transferring data to the
host computer.
Содержание Data Translation DT9857
Страница 1: ...DT9857 and DT9857E UM 25656 M User s Manual Title Page ...
Страница 4: ......
Страница 10: ...Contents 10 ...
Страница 14: ...About this Manual 14 ...
Страница 15: ...15 1 Overview Hardware Features 16 Supported Software 19 Supported Accessories 22 Getting Started Procedure 24 ...
Страница 25: ...Part 1 Getting Started ...
Страница 26: ......
Страница 40: ...Chapter 2 40 ...
Страница 61: ...61 4 Verifying the Operation of a Module Select the Device 63 Acquire Data from an Analog Output Channel 65 ...
Страница 64: ...Chapter 4 64 ...
Страница 71: ...Part 2 Using Your Module ...
Страница 72: ......
Страница 126: ...Chapter 6 126 ...
Страница 127: ...127 7 Troubleshooting General Checklist 128 Technical Support 130 If Your Module Needs Factory Service 131 ...
Страница 132: ...Chapter 7 132 ...
Страница 140: ...Chapter 8 140 ...
Страница 180: ...Appendix B 180 ...
Страница 181: ...181 C Register Level Programming Writing to the EEPROM Register 182 ...
Страница 184: ...Appendix C 184 ...
Страница 192: ...Index ...