Measurement-computing PC104-DAS16JR/12 Manuel d'utilisateur télécharger pdf (Page 23)

8254 COUNTER 1 DATA

BASE ADDRESS + 13 30Dh, 781 decimal

D1D2D3D4D5D6D7D8

01234567

8254 COUNTER 2 DATA

BASE ADDRESS + 14 30Eh, 782 decimal

D1D2D3D4D5D6D7D8

01234567

Because each counter will count as high as 65,535, loading or reading the counter data

is a multi-step process. Refer to the 82C54 data sheet for details regarding its

programming. The data sheet is available at:

http://www.measurementcomputing.com/PDFmanuals/82C54.pdf

8254 COUNTER CONTROL

BASE ADDRESS + 15 30Fh, 783 decimal

D1D2D3D4D5D6D7D8

01234567

This register controls the operation and loading/reading of the counters. Refer to the

82C54 data sheet for programming details.

3.10 ANALOG INPUTS

Analog signals connected to the analog inputs are first fed into the two HI-0508

analog multiplexers (MUXs). A MUX's function is to select one of the inputs and

connect that input to the MUX output. One of these MUX chips connects CH0-CH7

high inputs. The other connects CH0-CH7 Low input (differential input mode) or

CH8-CH15 High inputs (single ended mode) depending on the state of the channel

configuration switch marked 8/16.

From the output of the MUX, the analog signal is fed into a programmable differential

amplifier.

The A/D converter chip has an integral sample & hold circuit, greatly simplifying

design and improving signal integrity. The A/D converter is capable of sampling rates

to 330 kHz but the DMA transfer circuitry of the personal computer's 8-bit bus is

limited to a maximum synchronous transfer rate of less than the maximum A/D rate.

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Measurement-computing PC104-DAS16JR/12 Manuel d'utilisateur Page 23