Datasheet

SDA
SCL
1 2 76 8 9 1 2 3-8 8 9
Slave Address
MSB
Repeated If More Bytes Are Transferred
R/W
Direction
Bit
Acknowledgement
Signal from
Receiver
Acknowledgement
Signal from
Receiver
START
Condition
ACK
ACK
STOP Condition
or Repeated
START Condition
ADS7830
www.ti.com SBAS302C –DECEMBER 2003–REVISED OCTOBER 2012
Figure 14. Basic Operation of the ADS7830
Address Byte Command Byte
MSB 6 5 4 3 2 1 LSB MSB 6 5 4 3 2 1 LSB
1 0 0 1 0 A1 A0 R/W SD C2 C1 C0 PD1 PD0 X X
The address byte is the first byte received following The ADS7830 operating mode is determined by a
the START condition from the master device. The command byte which is illustrated above.
first five bits (MSBs) of the slave address are factory
SD: Single-Ended/Differential Inputs
pre-set to 10010. The next two bits of the address
0: Differential Inputs
byte are the device select bits, A1 and A0. Input pins
1: Single-Ended Inputs
(A1-A0) on the ADS7830 determine these two bits of
the device address for a particular ADS7830. A
C2 - C0: Channel Selections
maximum of four devices with the same pre-set code
can therefore be connected on the same bus at one
PD1: Power-Down
time.
0: Power-Down Selection
X: Unused
The A1-A0 Address Inputs can be connected to V
DD
or digital ground. The device address is set by the
See Table 1 for a power-down selection summary.
state of these pins upon power-up of the ADS7830.
See Table 2 for a channel selection control summary.
The last bit of the address byte (R/W) defines the
operation to be performed. When set to a ‘1’ a read
Table 1. Power-Down Selection
operation is selected; when set to a ‘0’ a write
PD1 PD0 DESCRIPTION
operation is selected. Following the START condition
0 0 Power Down Between A/D Converter Conversions
the ADS7830 monitors the SDA bus, checking the
0 1 Internal Reference OFF and A/D Converter ON
device type identifier being transmitted. Upon
1 0 Internal Reference ON and A/D Converter OFF
receiving the 10010 code, the appropriate device
1 1 Internal Reference ON and A/D Converter ON
select bits, and the R/W bit, the slave device outputs
an acknowledge signal on the SDA line.
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