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Principles of Operation
27
Output Filters
Note:
Output filters are supported on the DT9841, DT9841E, and DT9841-VIB modules only.
Each analog output channel on the DT9841, DT9841E, or DT9841-VIB supports a
software-selectable four-pole 5 kHz filter or a four-pole 20 kHz filter. Both are Bessel filters
and are useful if you want to smooth the analog output values. For fast clock rates, it is
recommended that you use the 20 kHz filter. For slow clock rates, it is recommended that you
use the 5 kHz filter.
On power-up or reset, no filter is used.
Data Format
The analog output data encoding used by the DT9841, DT9841E, an DT9841-VIB modules is
floating point. The data is 32-bit wide and left justified; the right eight bits are filled with
zeros.
The DT9842/2 and DT9842/8 modules use twos complement data encoding. The data is 32-bit
wide and left justified; the right 16 bits are filled with zeros.
You can use software to convert a voltage value into a twos complement code.
Data Transfer
The module packs 32 bits into each transfer. The board generates an interrupt (EXT_INT5)
after the data in the analog output channel has been output. For 100 kHz operation, both
analog output channels must then be updated with the next value to write within 10
μ
s.
For the DT9841, DT9841E, and DT9841-VIB modules, analog output data must always be
output as two 32-bit words: channels 0, then channel 1. The data is clocked into the internal
serial output register on the second word address. The initial value must be the code for 0 V
output to prevent glitching after power up.
For the DT9842/2 and DT9842/8, when new data is written to any of the analog output data
registers, all of the analog output channels are updated on the next clock cycle. For example,
assume that you write a new value to analog output channel 0. On the next clock cycle,
channel 0 is updated with the new value you specified, and all the other analog output
channels are updated with the existing values in the corresponding data registers.
Summary of Contents for DT9840 Series
Page 1: ...DT9840 Series UM 19197 T User s Manual Title Page ...
Page 4: ......
Page 44: ...Chapter 1 44 ...
Page 76: ...Chapter 2 76 ...
Page 98: ...Appendix A 98 ...
Page 124: ...Appendix B 124 ...