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VL-12CT96/7 Analog & Digital I/O Card
5-1
Operation
This section describes how to operate the VL-12CT96/7. Analog input, analog output, and digital I/O
are discussed. Code examples written in 80188 assembly language are included in the next section.
Analog Input
Polled Mode Analog Input
Polled mode operation is the simplest method of analog input. In this mode, software is in control of
the analog input process at all times. It is the responsibility of the CPU to start each new A/D
conversion as desired, and to read the digital results upon completion.
Polled Mode Steps
• Channel selection
• Trigger A/D conversion
• Wait until done
• Read data
Channel selection
Output the desired channel number to the SELECT register. See page 4-4 for further information.
After the first channel selection, this step can be skipped for multiple conversions of the same channel.
This will eliminate the settling delay which is inserted every time the SELECT register is written to.
A word-wide output instruction to this register (out dx,ax) also writes into the CONVERT register
causing channel addressing and triggering with one CPU instruction.
Trigger A/D conversion
Output to the CONVERT register. The register is data insensitive, any value written to it will start
an A/D conversion. See page 4-5 for further information.
Wait until done
Read the STATUS register repeatedly until the Done bit is set to “1.” See page 4-6 for further
information.
Read data
Input from the ADCLO register first, followed by the ADCHI register. A word-wide input instruction
from the ADCLO register (in ax,dx) will fetch data from both the registers in the proper sequence. See
page 4-7 for further information.
Operation
Содержание VL-12CT96
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