
AD7992
–12–
REV. PrH
PRELIMINARY TECHNICAL DATA
INTERNAL REGISTER STRUCTURE
The AD7992 contains eleven internal registers, as shown
in Figure 9, that are used to store conversion results, high
and low conversion limits, and to configure and control
the device. Ten are data registers and one is an address
pointer register.
Figure 9. AD7992 Register Structure
Each data register has an address which is pointed to by
the Address Pointer register when communicating with it.
The Conversion Result Register is the only data register
that is read only.
Table II. Address Pointer Register
C4
C3
C2
C1
P3
P2
P1
P0
0
0
0
0
Register Select
Table III. AD7992 Register Addresses
P3
P2
P1
P0
Registers
0
0
0
0
Conversion Result Register (Read)
0
0
0
1
Alert Status Register (Read/Write)
0
0
1
0
Configuration Register (Read/Write)
0
0
1
1
Cycle Timer Register (Read/Write)
0
1
0
0
DATA
LOW
Reg CH1 (Read/Write)
DATA
HIGH
Reg CH1 (Read/Write)
Hysteresis Reg CH1 (Read/Write)
0
1
0
1
0
1
1
0
0
1
1
1
DATA
LOW
Reg CH2 (Read/Write)
DATA
HIGH
Reg CH2 (Read/Write)
Hysteresis Reg CH2 (Read/Write)
1
0
0 0
1
0
0 1
ADDRESS POINTER REGISTER
The Address Pointer register itself does not have, nor does
it require, an address, as it is the register to which the first
data byte of every Write operation is written automatically.
The Address Pointer Register is an 8-bit register in which
the four LSBs are used as pointer bits to store an address
that points to one of the data registers of the AD7992,
while the four MSBs are used as command bits when us-
ing Mode 2 (see Modes of Operation section). The first
byte following each write address is the address of one of
the data registers, which is stored in the Address Pointer
Register, and selects the data register to which subsequent
data bytes are written. Only the four LSBs of this register
are used to select a data register. On Power up the Ad-
dress Point register contains all 0’s, therefore it is pointing
to the Conversion Result Register.
CONFIGURATION
REGISTER
ADDRESS
POINTER
REGISTER
SERIAL BUS INTERFACE
SDA
SCL
D
A
T
A
DATALOW
REGISTER CH2
DATAHIGH
REGISTER CH2
DATALOW
REGISTER CH1
HYSTERESIS
REGISTER CH1
DATAHIGH
REGISTER CH1
CYCLE TIMER
REGISTER
ALERT STATUS
REGISTER
CONVERSION
RESULT REGISTER
HYSTERESIS
REGISTER CH2
CONFIGURATION REGISTER
The Configuration Register is an 8-bit read/write register that is used to set the operating modes of the AD7992. The
MSB is used, and is a Don’t Care bit. The bit functions are outlined in Table IV.
Table IV. Configuration Register Bit Function Description
D7
D6
D5
D4
D3
D2
D1
D0
DONTC Single/Dual CH2
CH1
FLTR
ALERT EN
BUSY/
ALERT
ALERT/BUSY POLARITY
0*
0*
0*
0*
1*
0*
0*
0*
*Default settings at Power-up