MAX1258 Maxim Integrated Products, MAX1258 Datasheet - Page 28

• Manufacturer Part Number: MAX1258
• Description: Multichannel ADCs/DACs
• Manufacturer: Maxim Integrated Products

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Table 8. Unipolar/Bipolar Channel Function
Table 9. ADC Averaging Register*
12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
The final 2 bits (LSBs) of the setup register control the
unipolar-/bipolar-mode address registers. Set
DIFFSEL[1:0] = 10 to write to the unipolar-mode regis-
ter. Set bits DIFFSEL[1:0] = 11 to write to the bipolar-
mode register. In both cases, the setup command byte
must be followed by 1 byte of data that is written to the
unipolar-mode register or bipolar-mode register. Hold
CS low and run 16 SCLK cycles before pulling CS high.
*See below for bit details.
28
REGISTER BIT
AVGON
UNIPOLAR-
BIT NAME
NSCAN1
NSCAN0
NSCAN1
______________________________________________________________________________________
0
1
1
1
1
MODE
AVGON
NAVG1
NAVG0
0
0
1
1
—
—
—
0
0
1
1
NAVG1
X
0
0
1
1
BIPOLAR-MODE
REGISTER BIT
NSCAN0
7 (MSB)
0 (LSB)
BIT
0
1
0
1
NAVG0
6
5
4
3
2
1
0
1
0
1
Unipolar/Bipolar Registers
0
1
0
1
X
Performs one conversion for each requested result.
Performs four conversions and returns the average for each requested result.
Performs eight conversions and returns the average for each requested result.
Performs 16 conversions and returns the average for each requested result.
Performs 32 conversions and returns the average for each requested result.
Set to zero to select ADC averaging register.
Set to zero to select ADC averaging register.
Set to one to select ADC averaging register.
Set to one to turn averaging on. Set to zero to turn averaging off.
Configures the number of conversions for single-channel scans.
Configures the number of conversions for single-channel scans.
Single-channel scan count. (Scan mode 10 only.)
Single-channel scan count. (Scan mode 10 only.)
Scans channel N and returns four results.
Scans channel N and returns eight results.
Scans channel N and returns 12 results.
Scans channel N and returns 16 results.
Unipolar single-ended
Unipolar differential
Unipolar differential
Bipolar differential
CHANNEL PAIR
FUNCTION
FUNCTION (APPLIES ONLY IF SCAN MODE 10 IS SELECTED)
If the last 2 bits of the setup register are 00 or 01, nei-
ther the unipolar-mode register nor the bipolar-mode
register is written. Any subsequent byte is recognized
as a new command byte. See Tables 6, 7, and 8 to pro-
gram the unipolar- and bipolar-mode registers.
Both registers power up at all zeros to set the inputs as
16 unipolar single-ended channels. To configure a
channel pair as single-ended unipolar, bipolar differen-
tial, or unipolar differential, see Table 8.
In unipolar mode, AIN+ can exceed AIN- by up to
V
bipolar mode, either input can exceed the other by up
to V
complement (see the ADC Transfer Functions section).
Write a command byte to the ADC averaging register to
configure the ADC to average up to 32 samples for
each requested result, and to independently control the
number of results requested for single-channel scans.
REF
REF
. The output format in unipolar mode is binary. In
/ 2. The output format in bipolar mode is two’s
FUNCTION
FUNCTION
ADC Averaging Register