AD7997_15 Datasheet, PDF (19/32 Pages) Analog Devices – 8-Channel, 10- and 12-Bit ADCs with IC Compatible Interface in 20-Lead TSSOP

AD7997/AD7998
CONFIGURATION REGISTER
The configuration register is a 16-bit read/write register that is used to set the operating mode of the AD7997/AD7998. The 4 MSBs of the
register are unused. The bit functions of all 12 LSBs of the configuration register are outlined in Table 9. A 2-byte write is necessary when
writing to the configuration register.
Table 9. Configuration Register Bits and Default Settings at Power-Up
D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1
ALERT BUSY/
DONTC DONTC DONTC DONTC CH8 CH7 CH6 CH5 CH4 CH3 CH2 CH1 FLTR EN
ALERT
0
0
0
0
0
0
0000001
0
0
D0
ALERT/BUSY
POLARITY
0
Table 10. Bit Function Descriptions
Bit
Mnemonic Comment
D11 to D4 CH8 to CH1
These 8-channel address bits select the analog input channel(s) to be converted. A 1 in any of Bits D11 to D4
selects a channel for conversion. If more than one channel bit is set to 1, the AD7997/AD7998 sequence
through the selected channels, starting with the lowest channel. All unused channels should be set to 0. Prior
to initiating a conversion, a channel or channels for conversion must be selected in the configuration register.
D3
FLTR
The value written to this bit of the control register determines whether the filtering on SDA and SCL is
enabled or is to be bypassed. If this bit is a 1, then the filtering is enabled; if it is a 0, the filtering is bypassed.
D2
ALERT EN
The hardware ALERT function is enabled if this bit is set to 1, and disabled if this bit is set to 0. This bit is used
in conjunction with the BUSY/ALERT bit to determine if the ALERT/BUSY pin acts as an ALERT or a BUSY
output (see Table 12).
D1
BUSY/ALERT This bit is used in conjunction with the ALERT EN bit to determine if the ALERT/ BUSY output, Pin 17, acts as
an ALERT or BUSY output (see Table 12), and if Pin 17 is configured as an ALERT output pin, if it is to be reset.
D0
BUSY/ALERT This bit determines the active polarity of the ALERT/BUSY pin regardless of whether it is configured as an
POLARITY
ALERT or BUSY output. It is active low if this bit is set to 0, and active high if set to 1.
Table 11. Channel Selection
D11 D10 D9 D8 D7 D6 D5 D4 Selected Analog Input Channel Comments
0
0
0
0
0
0
0
1
Convert on Channel 1 (VIN1)
0
0
0
0
0
0
1
0
Convert on Channel 2 (VIN2)
0
0
0
0
0
1
0
0
Convert on Channel 3 (VIN3)
0
0
0
0
1
0
0
0
Convert on Channel 4 (VIN4)
0
0
0
1
0
0
0
0
Convert on Channel 5 (VIN5)
0
0
1
0
0
0
0
0
Convert on Channel 6 (VIN6)
If more than one channel is
selected, the AD7997/AD7998
start converting on the selected
sequence of channels starting with
the lowest channel in the
sequence.
0
1
0
0
0
0
0
0
Convert on Channel 7 (VIN7)
1
0
0
0
0
0
0
0
Convert on Channel 8 (VIN8)
Table 12. ALERT/BUSY Function
D2
D1
ALERT/BUSY Pin Configuration
0
0
Pin does not provide any interrupt signal.
0
1
Pin configured as a BUSY output.
1
0
Pin configured as an ALERT output.
Resets the ALERT output pin, the Alert_Flag bit in the conversion result register, and the entire alert status register
1
1
(if any is active). If 1/1 is written to Bits D2/D1 in the configuration register to reset the ALERT pin, the Alert_Flag bit,
and the alert status register, the contents of the configuration register read 1/0 for D2/D1, respectively, if read back.
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