ADLINK ACL-8111 - Manual (Page 33)

Operation Theorem • 27
4.1.1 A/D Conversion Procedure
The A/D conversion is starting by a trigger source, then the A/D converter will
start to convert the signal to a digital value. The ACL-8111 provides three
trigger modes, see section 4.1.2.
The DRDY bit in the A/D data register (Base+5) will become to 0 once the
A/D conversion is completed and data on the Base+4 and Base+5 are ready.
A read data command on BASE+4 will automatically reset the DRDY bit to be
1 which means data is not ready on the Base+4 and Base+5. The A/D data
should be transferred into PC's memory for further using. The ACL-8111
provides three data transfer modes that allow users to optimize the DAS
system. Refer to section 4.1.3 for data transfer modes.
4.1.2 A/D Clock Sources (Trigger Modes)
In the ACL-8111, two Internal or one external clock sources can trigger A/D
conversion. The two internal sources are the software trigger and the timer
pacer trigger, which is controlled by the A/D operation mode control register
(BASE+11). The A/D operation modes combine the AD clock sources and
the data transfer mode together. Please also refer to the next section for
detail data transfer modes. The available operation modes include:
• Software trigger and software polling transfer
• Internal timer pacer and interrupt transfer
• Internal timer pacer and software polling transfer
• External trigger and interrupt transfer
• External trigger and software polling transfer
Three AD clock sources (or trigger sources) are available in the ACL-8111.
Software trigger
The trigger source is software controllable in this mode. That is, the A/D
conversion is starting when any value is written into the software trigger
register (BASE+12). Under this mode, the timing of the A/D conversion is
fully controlled by software, it is suitable for low speed A/D conversion.
However, it is difficult to control the fixed A/D conversion rate except a timer
interrupt service routine is used and the software trigger is programmed
inside the interrupt service routines.