Rainbow Electronics ADC12041 - Manual (Page 24)

Features and Operating Modes
(Continued)
SYNC-IN Synchronous
For the SYNC-IN case it is assumed that a series of SYNC
pulses at the desired sampling rate are applied at the SYNC
pin of the ADC12041
8-bit mode A write to the ADC12041 should set the SYNC
bit write the START command and clear the BW bit The
programmed acquisition time in bits b
1 and b 0 is a don’t
care condition in the SYNC-IN mode
A rising edge on the SYNC pin or the second rising edge of
two consecutive reads from the ADC12041 will force the
RDY signal high It is recommended that the action of read-
ing from the ADC12041 (not the rising edge of the SYNC
signal) be used to raise the RDY signal This will ensure that
the conversion result is read during the acquisition period of
the next conversion cycle eliminating a read from the
ADC12041 while it is performing a conversion Noise gener-
ated by accessing the ADC12041 while it is converting may
degrade the conversion result In the SYNC-IN mode only
the rising edge of the SYNC signal will begin a conversion
cycle The rising edge of the SYNC also ends the acquisi-
tion period The acquisition period begins after the falling
edge of the RDY signal The input is sampled until the rising
edge of the SYNC pulse at which time the signal will be
held and conversion begins The RDY signal will go low
when the conversion is done and a new operational com-
mand may be written into the Configuration register at this
time if needed Two consecutive read cycles are required to
retrieve the entire 13-bit conversion result from the
ADC12041’s Data register The first read will place the low-
er byte of the conversion result contained in the Data regis-
ter on the data bus The second read will place the upper
byte of the conversion result stored in the Data register on
the data bus With the START command in the configuration
register the rising edge of the second read pulse will raise
the RDY signal high and begin a conversion cycle following
a rising edge on the SYNC pin
13-bit mode The SYNC bit and the BW bit should be set
and the START command issued with a write to the
ADC12041 A rising edge on the SYNC pin or on the RD pin
will force the RDY signal high It is recommended that the
action of reading from the ADC12041 (not the rising edge of
the SYNC signal) be used to raise the RDY signal This will
ensure that the conversion result is read during the acquisi-
tion period of the next conversion cycle eliminating a read
from the ADC12041 while it is performing a conversion
Noise generated by accessing the ADC12041 while it is
converting may degrade the conversion result In the SYNC-
IN mode only the rising edge of the SYNC signal will begin
a conversion cycle The RDY signal will go low when the
conversion cycle is done The acquisition time is controlled
by the SYNC signal The acquisition period begins after the
falling edge of the RDY signal The input is sampled until the
rising edge of the SYNC pulse at which time the signal will
be held and conversion begins The RDY signal will go low
when the conversion is done and a new operational com-
mand may be written into the Configuration register at this
time if needed With the START command in the Configura-
tion register a read from the ADC12041 will place the entire
conversion result stored in the Data register on the data bus
and the rising edge of the read pulse will force the RDY
signal high
STANDBY COMMAND
8-bit mode A write to the ADC12041 should clear the BW
bit and issue the Standby command
13-bit mode A write to the ADC12041 should set the BW bit
and issue the Standby command
RESET
The RESET command places the ADC12041 into a ready
state and forces the RDY signal low The RESET command
can be used to interrupt the ADC12041 while it is performing
a conversion full-calibration or auto-zero cycle It can also
be used to get the ADC12041 out of the standby mode
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