Xycom XVME-500, Manual

Page: 49 / 104

XVME-500/590 Manual
February, 1988
3.3.1
Status/Control Register (Base + 8lH)
The status/control register provides the control signals required to reset the
module, enable interrupts, start conversion and select the mode of operation. The
four modes of operation are single, sequential, random channel and external trigger.
Writing to the status/control register can: initiate an A/D conversion, select an A/D
conversion mode, reset the module, and enable module interrupts to the VMEbus.
Reading from the status/control register can indicate: whether or not a conversion
is in progress (or when a conversion is complete), and if there are interrupts
pending. Table 3-1 describes the functions of the status/control bits.
Table 3-1. Status/Control Register
3.3.1.1
Bit No.
Function
I
Status
Control
0 - -
1 -
2 Interrupt Pending No Connection .
3
Interrupt Enable Interrupt Enable
4 Board Reset Board Reset
5 Mode 0 M o d e 0
6 Mode 1 Mode 1
7
A/D Busy
Convert
Status/Control Register Bit Definitions
D 7 This bit acts as a ‘busy’ flag, showing when an A/D conversion is in
progress. A logic ‘1’ at this location indicates the analog input
module is in the process of making a conversion. The level of this
bit should be checked prior to start-up of new conversions, or the
in-progress conversion could be ruined.
Writing a logic ‘1’ to this bit “forces” a conversion to start.
This method of forcing a conversion works in any of the four A/D
data conversion modes.
D6 & 5: These are read/write bits that describe which of the four analog
modes the module will operate within. Table 3-2 shows the four
input mode options.
3-4
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