Xycom XVME 590, Руководство пользователя

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XVME-500/590 Manual
February, 1988
N O T E
The LSB (Least Significant Bit) represents the
change in input voltage that results in an increase
or decrease of the binary code by one count.
The
LSB is derived from the full range of either current
or voltage (Vfsr), divided by the maximum conversion
resolution (i.e., 12 bits or 4096 in binary counts).
Thus, the value of one LSB can be determined by the
following:
Unipolar LSB = Vfsr
4096
Bipolar LSB = (+Vf sr)-(-Vf sr)
4096
The following list shows the value of l-LSB for each range:
= 2.44 14mV
= 4.8828mV
0 - 1OV = 2.4414mV
3.4 A/D CONVERSION PRINCIPALS
Any procedure for configuring the Analog Input Module to convert analog inputs to
digital data must include the following elements:
1)
2)
3)
4)
5)
Jumper Configurations (see Chapter 2) Jumpers must be configured for
the desired interrupt level, input type (DI or SE; and bipolar or unipolar),
input voltage range, input gain range and input binary data format
(straight binary, offset binary or two’s complement).
Initialization
(see Section 3.3.3)
Gain RAM must be initialized
(programmed) by writing to the gain/channel register.
Calibration (see Chapter 4) Calibrations must be performed at installation
and whenever adjustments are made to change gains and ranges.
This
will help to assure accurate conversion of data by the analog input
module.
Conversion Mode Selection (see Sections 3.4.1 and 3.1.1) One of four
A/D conversion modes must be selected by writing to the status/control
register.
Conversion Initiation (see Sections 3.3.3 and 3.4.1) The A/D conversion
process must be initiated.
A conversion may be ‘force’ started, initiated
by reading the low order byte of the A/D Data Register in two of the
four modes, or started via External Trigger.
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