Programming
Chapter 4
AT-MIO-16D User Manual
4-68
© National Instruments Corporation
checked every time the Status Register is read to check the CONVAVAIL bit. If either of these
error conditions occurs, the data acquisition operation stops.
An overflow condition occurs if more than 512 A/D conversions have been stored in the A/D
FIFO without the A/D FIFO being read; that is, the A/D FIFO is full and cannot accept any more
data. This condition occurs if the software loop reading the A/D FIFO Register is not fast
enough to keep up with the A/D conversion rate. When an overflow occurs, at least one A/D
conversion result is lost. An overflow condition has occurred if the OVERFLOW bit in the
Status Register is set.
An overrun condition occurs if a second A/D conversion is initiated before the previous
conversion is finished. This condition may result in one or more missing A/D conversions. This
condition occurs if the sample interval is too small (sample rate is too high). An overrun
condition has occurred if the OVERRUN bit in the Status Register is set.
Scanned data acquisition requires slower acquisition rates than single-channel data acquisition
because signals must settle each time channels are switched. See Table 4-4 for the maximum
recommended multiple-channel data acquisition rates. The rates in Table 4-4 refer to typical
settling accuracies of 0.5 LSBs of the final value.
Table 4-4. Multiple-Channel Data Acquisition Rates
Gain
Data Acquisition Rate
1, 2, 4, 8
100 ksamples/sec
10
100 ksamples/sec
100
70 ksamples/sec
500
20 ksamples/sec
Both the OVERFLOW and OVERRUN bits in the Status Register are cleared by writing to the
A/D Clear Register.
External Timing Considerations for Scanned Data Acquisition
After you follow the programming instructions listed previously under External Timing
Considerations for Multiple A/D Conversions, complete these additional steps:
1. Set up the analog channel and gain sequence as given above.
2. Set the SCANEN bit in Command Register 1.
3. Set the multiplexer counter to 0 before starting the data acquisition operation.
Resetting the Hardware after a Data Acquisition Operation
After a data acquisition operation is complete, if no errors occurred and the sample count was
less than or equal to 10000 hex, then the AT-MIO-16D is left in the same state as it was at the
beginning of the data acquisition operation. The counters do not need to be reprogrammed;
another data acquisition operation begins when a trigger is received. If the next data acquisition
Содержание AT-MIO-16D
Страница 16: ......
Страница 23: ......
Страница 185: ......
Страница 206: ......
Страница 207: ......
Страница 208: ......
Страница 209: ......
Страница 210: ......
Страница 211: ......
Страница 212: ......
Страница 213: ......
Страница 214: ......
Страница 215: ......
Страница 216: ......
Страница 217: ......
Страница 218: ......
Страница 219: ......
Страница 220: ......
Страница 221: ......
Страница 222: ......
Страница 223: ......
Страница 224: ......
Страница 225: ......
Страница 226: ......
Страница 227: ......
Страница 228: ......
Страница 229: ......
Страница 230: ......
Страница 231: ......
Страница 232: ......
Страница 233: ......
Страница 234: ......
Страница 235: ......
Страница 236: ......
Страница 237: ......
Страница 238: ......
Страница 239: ......
Страница 240: ......
Страница 241: ......
Страница 242: ......
Страница 243: ......
Страница 244: ......
Страница 246: ......
Страница 247: ......
Страница 248: ......
Страница 249: ......
Страница 250: ......
Страница 251: ......
Страница 252: ......
Страница 253: ......
Страница 254: ......
Страница 255: ......
Страница 256: ......
Страница 257: ......
Страница 258: ......
Страница 259: ......
Страница 260: ......
Страница 261: ......