Xycom XVME 590 Manual page 61

XVME-500/590 Manual
February, 1988
3.4.1.2
Sequential Channel Mode
In the sequential-channel mode, the module will automatically increment the channel
by one and initiate a conversion on the next channel (previous channel + 1). This
will occur after the low order A/D input byte (base + 87H) has been read. A
conversion can be initiated in this mode without incrementing the channel number
by writing a logic '1' to bit D7 of the status/control register (by forcing a
conversion).
Procedure
Write a control byte to the status/control register (base + 81H) that sets
1)
bit D5 to logic '1' and bit D6 to logic '0'.
2) Select a starting channel by writing the channel number to bits D0 thru
D4 of the gain/channel register (base + 85H). Assuming that the cor-
responding Gain RAM was properly initialized (programmed) after power-
up, the gain will not have to be rewritten at this time (unless a change
in gain is desired).
To initiate the first conversion, write a control byte to the status/control
3)
register that sets bit D7 to logic '1'.
on the specified starting channel without incrementing the channel
number. Then, by reading the low order A/D data byte (base + 87H), the
channel number will be incremented by one; and the next conversion will
be started.
The first conversion may also be initiated by doing a
"dummy" read of the low order
method, though, will increment the channel number
written to the Gain/Channel Register in step 2.
When the dummy read method is used to initiate the
first conversion, the channel offset may be corrected
by specifying a channel number (in step 2) which is
one less than the desired starting channel number
(e.g., if the first channel
then channel 31 should
channel).
Wait until the conversion is complete (i.e., check the busy flag (bit D7)
4)
of the status/control register, or use interrupts).
Read the results of the conversion from the A/D data registers -- high
5)
byte before low byte (base + 86H before base + 87H). After the low byte
is read, a new conversion will automatically be initiated on the next
channel (previous channel + 1).
This action will force a conversion '
NOTE
input byte. This
A/D
conversion is channel 0
for
entered as the starting
be
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