Omega Engineering OME-A8111 manual 1 A/D conversion flow, 2 A/D Conversion Trigger Modes

2.7.1 A/D conversion flow

Then the user must decide which A/D conversion mode will be used. The software driver supports three different modes. The user can control the A/D conversion by polling mode very easily (sec. 2.4.9). It is recommended to use the software driver if using interrupt or DMA mode.

The analog input signals come from CN1.

The multiplexer can accept 8 single-ended lines into the gain control module. The gain control module also needs settling time if the gain control code changed. Because the software doesn’t monitor the settling time, the user should reserve enough settling time

if switching from one channel to the next (sec. 2.4.6).

The output of the gain control module feeds into the A/D converter. The A/D converter

needs a trigger signal to start an A/D conversion cycle. The OME-A-8111 supports software trigger or pacer trigger mode.

2.7.2A/D Conversion Trigger Modes

OME-A-8111 supports two trigger modes.

1 : Software Trigger :

Writes any value to the A/D software trigger control register, BASE+A, will initiate an A/D conversion cycle. This mode is very simple but very difficult to control the sampling rate.

2 : Pacer Trigger Mode :

The block diagram of the pacer timer is shown in section 2.6. The pacer timer can give very precise sampling rates.

OME-A-8111 Hardware Manual (ver.1.1, Jul/2003) 22