Omega Engineering OME-A8111 manual 9 A/D Software Trigger Control Register

The pacer trigger can control the sampling rate very precisely. So the converted data can be used to reconstruct the waveform of the analog input signal. In pacer trigger mode, the pacer timer will periodically generate trigger signals to the A/D converter. This converted data can be transfer to the CPU by polling or interrupt or DMA transfer method.

The software driver provides three polling or interrupt-transfermethods. The polling subroutine, A8111_AD_PollingVar() or A822_AD_PollingArray(), sets the A/D mode control register to 0x01. This control word means software trigger and polling transfer. The interrupt subroutine, A822_AD_INT_START(…), sets the A/D mode control mode register to ox06. This control word means pacer trigger and interrupt transfer. The interrupt subroutine, A822_AD_DMA_START(…), sets the A/D mode control register to 0x06 This control word means pacer trigger and DMA transfer.

2.4.9A/D Software Trigger Control Register

(WRITE)	Base+C : A/D Software Trigger Control Register Format
Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
X	X	X	X	X	X	X	X

X=don‘t care, XXXXXXXX=any 8 bits data is validate

The A/D converter can be triggered by software trigger or pacer trigger. Detailed information is given in sec.2.4.8 and 2.7. Writing any value to address BASE+C will generate a trigger pulse to the A/D converter and initiate an A/D conversion operation. The address BASE+5 offers a ready bit to indicate that an A/D conversion is complete.

The software driver uses this control word to detect the OME-A-8111 hardware board. The software initiates a software trigger and checks the ready bit. If the ready bit cannot clear to zero in a fixed time, the software driver will return an error message. If there is an error in the I/O BASE address setting, the ready bit will not be cleared to zero. The software driver, A8111_CheckAddress(), uses this method to detect the status of the I/O BASE address setting.

OME-A-8111 Hardware Manual (ver.1.1, Jul/2003) 17