Adlink ACL-8111 Manual do Utilizador descarregar pdf (Página 33)

Operation Theorem

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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

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.

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Adlink ACL-8111 Manual do Utilizador Página 33