AD7795_15 Datasheet, PDF (25/37 Pages) Analog Devices – 6-Channel, Low Noise, Low Power

AD7794/AD7795
DATA REGISTER
RS2, RS1, RS0 = 0, 1, 1; Power-On/Reset =
0x0000(AD7795), 0x000000 (AD7794)
The conversion result from the ADC is stored in this data
register. This is a read-only register. On completion of a read
operation from this register, the RDY bit/pin is set.
ID REGISTER
RS2, RS1, RS0 = 1, 0, 0; Power-On/Reset = 0xXF
The identification number for the AD7794/AD7795 is stored in
the ID register. This is a read-only register.
IO REGISTER
RS2, RS1, RS0 = 1, 0, 1; Power-On/Reset = 0x00
The IO register is an 8-bit read/write register that is used
to enable the excitation currents and select the value of the
excitation currents.
Table 21 outlines the bit designations for the IO register. IO0
through IO7 indicate the bit locations. IO denotes that the bits
are in the IO register. IO7 denotes the first bit of the data
stream. The number in brackets indicates the power-on/reset
default status of that bit.
IO7 IO6
0(0) IOEN(0)
IO5
IO2DAT(0)
IO4
IO1DAT(0)
IO3
IEXCDIR1(0)
IO2
IEXCDIR0(0)
IO1
IEXCEN1(0)
IO0
IEXCEN0(0)
Table 21. IO Register Bit Designations
Bit No.
Mnemonic
Description
IO7
0
This bit must be programmed with a Logic 0 for correct operation.
IO6
IOEN
Configures Pin AIN6(+)/P1 and Pin AIN6(−)/P2 as analog input pins or digital output pins. When this
bit is set, the pins are configured as Digital Output Pin P1 and Digital Output Pin P2. When this bit is
cleared, these pins are configured as Analog Input Pin AIN6(+) and Analog Input Pin AIN6(−).
IO5 to IO4 IO2DAT/IO1DAT
P2/P1 Data. When IOEN is set, the data for Digital Output Pin P1 and Digital Output Pin P2 is written
to Bit IO2DAT and Bit IO1DAT.
IO3 to IO2 IEXCDIR1 to IEXCDIR0 Direction of Current Sources Select Bits.
IEXCDIR1 IEXCDIR0 Current Source Direction
0
0
Current Source IEXC1 connected to Pin IOUT1. Current Source IEXC2
connected to Pin IOUT2.
0
1
Current Source IEXC1 connected to Pin IOUT2. Current Source IEXC2
connected to Pin IOUT1.
1
0
Both current sources connected to Pin IOUT1. Permitted only when the
current sources are set to 10 μA or 210 μA.
1
1
Both current sources connected to Pin IOUT2. Permitted only when the
current sources are set to 10 μA or 210 μA.
IO3 to IO2 IEXCEN1 to IEXCEN0
These bits are used to enable and disable the current sources. They also select the value of the
excitation currents.
IEXCEN1 IEXCEN0 Current Source Value
0
0
Excitation currents disabled
0
1
10 μA
1
0
210 μA
1
1
1 mA
Rev. D | Page 24 of 36