Datasheet

AD7730/AD7730L
–15–
Data Register (RS2–RS0 = 0, 0, 1); Power On/Reset Status: 000000 Hex
The Data Register on the part is a read-only register which contains the most up-to-date conversion result from the AD7730. Fig-
ure 5 shows a flowchart for reading from the registers on the AD7730. The register can be programmed to be either 16 bits or 24bits
wide, determined by the status of the WL bit of the Mode Register. The RDY output and RDY bit of the Status Register are set low
when the Data Register is updated. The RDY pin and RDY bit will return high once the full contents of the register (either 16bits or
24 bits) have been read. If the Data Register has not been read by the time the next output update occurs, the RDY pin and RDY bit
will go high for at least 100 × t
CLK IN
, indicating when a read from the Data Register should not be initiated to avoid a transfer from
the Data Register as it is being updated. Once the updating of the Data Register has taken place, RDY returns low.
If the Communications Register data sets up the part for a write operation to this register, a write operation must actually take place
in order to return the part to where it is expecting a write operation to the Communications Register (the default state of the inter-
face). However, the 16 or 24 bits of data written to the part will be ignored by the AD7730.
Mode Register (RS2–RS0 = 0, 1, 0); Power On/Reset Status: 01B0 Hex
The Mode Register is a 16-bit register from which data can be read or to which data can be written. This register configures
the operating modes of the AD7730, the input range selection, the channel selection and the word length of the Data Register.
Table X outlines the bit designations for the Mode Register. MR0 through MR15 indicate the bit location, MR denoting the bits are
in the Mode Register. MR15 denotes the first bit of the data stream. The number in brackets indicates the power-on/reset default
status of that bit. Figure 5 shows a flowchart for reading from the registers on the AD7730 and Figure 6 shows a flowchart for writ-
ing to the registers on the part.
Table X. Mode Register
MR15 MR14 MR13 MR12 MR11 MR10 MR9 MR8
MD2 (0) MD1 (0) MD0 (0) B/U (0) DEN (0) D1 (0) D0 (0) WL (1)
MR7 MR6 MR5 MR4 MR3 MR2 MR1 MR0
HIREF (1) ZERO (0) RN1 (1) RN0 (1) CLKDIS (0) BO (0) CH1 (0) CH0 (0)
Bit Bit
Location Mnemonic Description
MR15–MR13 MD2–MD0 Mode Bits. These three bits determine the mode of operation of the AD7730 as outlined in
Table XI. The modes are independent, such that writing new mode bits to the Mode Register
will exit the part from the mode in which it is operating and place it in the new requested mode
immediately after the Mode Register write. The function of the mode bits is described in more
detail below.
Table XI. Operating Modes
MD2 MD1 MD0 Mode of Operation
0 0 0 Sync (Idle) Mode Power-On/Reset Default
0 0 1 Continuous Conversion Mode
0 1 0 Single Conversion Mode
0 1 1 Power-Down (Standby) Mode
1 0 0 Internal Zero-Scale Calibration
1 0 1 Internal Full-Scale Calibration
1 1 0 System Zero-Scale Calibration
1 1 1 System Full-Scale Calibration
REV. B