AXIOMTEK DASP-52282, Руководство пользователя

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DASP-52282 Card User’s Manual
Theorem of Operation
26
3.2 Acquisition Modes of Analog Input
DASP-52282 provides internal (software/ hardware) trigger
operation and external (hardware) trigger operation for data
acquisition application. The supported internal trigger operations
include a software polling mode and a hardware-clocked pacer
mode. To synchronize external event and data acquisition of the
DASP-52282, a series of external trigger mechanism, including
pre-rigger, middle trigger and post trigger is provided. The
operation mode of analog input of the DASP-52282 is described
in the following subsections.
3.2.1 Polling Mode
With polling mode operation, according to the user’s polling
command, DASP-52282 performs an AD conversion of user
specified analog input channel. To command DASP-52282 to
perform a polling operation, write BASE+0x16 and ADC will
convert one time. When AD conversion finish,
Pready
(BASE+0x02 Bit3) will be high.
3.2.2 Pacer Mode
Benefited by the double buffering mechanism and the auto-scan
mechanism, DASP-52282 can be operated at high sampling rate
up to 330KHz. Instead of polling (software-commanded AD
conversion), a series of hardware-clocked AD conversions can
be performed to acquire data. The hardware pacer clock can be
programmed from several Hz to 330KHz. With double buffering
mechanism, the host program can retrieve batch data from the
software buffer periodically. The only thing user need to consider
is to retrieve buffered data frequently enough to prevent from the
un-retrieved data in the buffer been overwritten. The functional
block diagram of pacer mode operation of DASP-52282 is
depicted as in following figure.
ADC
Analog Input
Digital Output
Convert Com m and
Trigger Logic
Tim er
Counter
Functional Block Diagram of Pacer Mode Operation of
DASP-52282