HP (Hewlett-Packard) PCI-9111DG/HR ユーザーズマニュアル
Operation Theorem
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It is possible to read A/D converted data without polling. The A/D
conversion time will not exceed 8.5
conversion time will not exceed 8.5
µ
s on PCI-9111 card. Hence, after
software trigger, the software can wait for a t least 8.5
µ
s then read the A/D
register without polling.
The data polling transferring is very suitable for the application need to
process AD data in real time. Especially when combining with the timer
interrupt generation, the timer interrupt service routine can use the data
polling method to get multi-channel A/D data in real time and under fixed
data sampling rate.
process AD data in real time. Especially when combining with the timer
interrupt generation, the timer interrupt service routine can use the data
polling method to get multi-channel A/D data in real time and under fixed
data sampling rate.
FIFO Half-Full Polling
The FIFO half-full polling mode is the most powerful AD data transfer
mode. The 1 K words FIFO can store up to 10.2 4 ms analog data under
100 KHz sampling rate (10.024ms = 1024/100 KHz). Theoretically, the
software can poll the FIFO every 10 ms without taking care how to trigger
A/D or transfer A/D data.
mode. The 1 K words FIFO can store up to 10.2 4 ms analog data under
100 KHz sampling rate (10.024ms = 1024/100 KHz). Theoretically, the
software can poll the FIFO every 10 ms without taking care how to trigger
A/D or transfer A/D data.
ADLINK recommend user to check your system to find out the user
software‘s priority in the special application. If the application software is
at the highest priority, to poll the FIFO every 10 ms is suitable. However,
the user‘s program must check the FIFO is full or empty every time
reading data.
software‘s priority in the special application. If the application software is
at the highest priority, to poll the FIFO every 10 ms is suitable. However,
the user‘s program must check the FIFO is full or empty every time
reading data.
To avoid this problem, the half-full polling method is used. If the A/D
trigger rate is 100KHz, the FIFO will be half-full (512 words) in 5.12 ms. If
the user‘s software checks the FIFO half full signal every 5 ms. When the
FIFO is not half-full, the software does not read data, because it is difficult
to know how much A/D data is stored in the FIFO and user must check
the FIFO empty bit every time reading data. When the FIFO is full, the
AD FIFO is overrun. This means the sampling rate is higher than users
expect or the polling rate is too slow, it is also possible due to your system
occupy the CPU resource thus reducing the polling rate. When the FIFO
is half-full and not full, the software can read one “block” (512 words) A/D
data without check the FIFO status. This method is very convenient to
read A/D in size of a “block” and it is benefit to software programming.
trigger rate is 100KHz, the FIFO will be half-full (512 words) in 5.12 ms. If
the user‘s software checks the FIFO half full signal every 5 ms. When the
FIFO is not half-full, the software does not read data, because it is difficult
to know how much A/D data is stored in the FIFO and user must check
the FIFO empty bit every time reading data. When the FIFO is full, the
AD FIFO is overrun. This means the sampling rate is higher than users
expect or the polling rate is too slow, it is also possible due to your system
occupy the CPU resource thus reducing the polling rate. When the FIFO
is half-full and not full, the software can read one “block” (512 words) A/D
data without check the FIFO status. This method is very convenient to
read A/D in size of a “block” and it is benefit to software programming.
Usually, the timer trigger is used under this mode, therefore the sampling
rate is fixed. The method also utilizes the minimum CPU resources
because it is not necessary to be highest priority. The other benefit is this
method will not use hardware interrupt resource. Therefore, the interrupt
is reserved for system clock or emergency external interrupt request. The
FIFO half-full polling method is the most powerful A/D data transfer
mode.
rate is fixed. The method also utilizes the minimum CPU resources
because it is not necessary to be highest priority. The other benefit is this
method will not use hardware interrupt resource. Therefore, the interrupt
is reserved for system clock or emergency external interrupt request. The
FIFO half-full polling method is the most powerful A/D data transfer
mode.