Xycom XVME 590, Manual

Page: 64 / 102

XVME-500/590 Manual
February, 1988
NOTE
A software reset (see Section 3.3.1.1) will reset the
flip-flop used to latch the external-trigger pulse, and
abort any conversion in progress.
If an external trigger occurs while the module is in any mode other than the
external-trigger mode, the trigger signal will be latched and a conversion will occur
as soon as the external-trigger mode is entered.
3.4.2 Interrupts
The analog input portion of the module can generate an interrupt to notify the host
that the A/D conversion is complete and the results are available.
The level and
vector generated by this interrupt are both user-selectable.
The following three steps must be performed in order to generate an interrupt:
1)
Interrupt level select jumpers must be configured to enable the module
IACK* handling circuitry (see Section 2.5.3).
2)
The Interrupt Vector Register (location base + 83H) must be loaded with
the required vector.
This vector register will be read by the interrupt
handler when the interrupt is acknowledged.
3)
Interrupts must be enabled via bit D2 in the’status/control register (see
Section 3.3.1.1).
At the completion of a conversion, an interrupt will be generated.
3.4.3 Current Loop Inputs
An A/D input will operate in a 4-20mA or 10-50mA current loop configuration with
the addition of an external current sensing resistor. The current sensing resistor
should be selected to generate a voltage within the predetermined, jumper-selected
voltage range (0-10V max.).
A voltage drop of less than IV will provide current of
less than 4mA, and would thus indicate improper operation of the current loop.
Typically, the resistors used would be:
A 500-ohm 1/2W for the 4-20mA configuration,
O R
A 200-ohm 1/2W for the l0-50mA configuration.
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