ICP DAS USA PCI-1202L User Manual page 97

PCI-1202/1602/180x Series Card
Multi-Function Boards
The A/D conversion data in FIFO are in the same sampling rate (refer to (1), (2), (3)).
For example,

the scan channel is 1 2  3

the pacer sampling rate is 330 k

We want a 110 k sampling rate for channel 1

We want a 55 k sampling rate for channel 2

We want a 11 k sampling rate for channel 3
The hardware will scan the analog data into FIFO as follows:
1,2,3,1,2,3,1,2,3,1,2,3,1,2,3,1,2,3......
 total 330 k
 every 1,1,1,1,1 is 110 k
 every 2,2,2,2,2 is 110 k
 every 3,3,3,3,3 is 110 k
The software has to fetch the 2,2,2,2,2 in 55 k, therefore the software averages the continue two 2
into one 2 to get 55 k as follows:
2,2, 2,2 2,2,
2, 2,
The software has to fetch the 3,3,3,3,3 in 11 k, therefore the software average the continue ten 3
into one 3 to get 11 k.
There are very heavy computation loads for the PC to execute the MagicScan function. These
computation loads are given as follows:
1. Averages the continue N data into one data to get different sampling rate data
2. Compares each A/D data with the HI/LO alarm limit
3. Saves the A/D data into memory if the save flag is enabled
The MagicScan function described in this section can be realized in Pentium-120 and Windows 95
without other running programs (like anti-virus of firewall).
Refer to Sec. 7.8.6 for driver source.
Refer to Chapter 11 for demo program.
Refer to Chapter 12 for performance evaluation
2,2
 55 k
2, 2,
User Manual/ Ver. 4.8/ Mar. 2015/ PMH-0014-48/ Page: 97