Datasheet

Frame1SlaveAddressByte
Frame2PointerAddressByte
1
StartBy
Master
ACKBy
ADS7924
ACKBy
ADS7924
1 9 1
Frame3RegisterDataByte
ACKBy
ADS7924
StopBy
Master
1
D7 D6 D5 D4 D3 D2 D1 D0
9
SDA
(Continued)
SCL
(Continued)
9
SDA
SCL
0 0 1 0
0 A0
(1)
R/W
0
(2)
0 0 P4
(3)
P3 P2 P1 P0 ¼
¼
ADS7924
SBAS482A –JANUARY 2010–REVISED MAY 2010 www.ti.com
Receive Mode:
least significant byte is then sent by the slave and is
followed by an acknowledgment from the master. The
In slave receive mode the first byte transmitted from
master may terminate transmission after any byte by
the master to the slave is the address with the R/W
not acknowledging or issuing a START or STOP
bit low. This byte allows the slave to be written to.
condition.
The next byte transmitted by the master is the
register pointer byte. The ADS7924 then
WRITING THE REGISTERS
acknowledges receipt of the register pointer byte. The
next two bytes are written to the address given by the
To access a write register from the ADS7924, the
register pointer. The ADS7924 acknowledges each
master must first write the appropriate value to the
byte sent. Register bytes are sent with the most
Pointer address. The Pointer address is written
significant byte first, followed by the least significant
directly after the slave address byte, low R/W bit, and
byte.
a successful slave acknowledgment. After the Pointer
address is written, the slave acknowledges and the
Transmit Mode:
master issues a STOP or a repeated START
condition. The MSB of the pointer address is the
In slave transmit mode, the first byte transmitted by
increment (INC) bit. When set to '1', the register
the master is the 7-bit slave address followed by the
address is automatically incremented after every
high R/W bit. This byte places the slave into transmit
register write which allows convenient writing of
mode and indicates that the ADS7924 is being read
multiple registers. Set INC to '0' when writing a single
from. The next byte transmitted by the slave is the
register. Figure 30 and Figure 31 show timing
most significant byte of the register that is indicated
examples.
by the register pointer. This byte is followed by an
acknowledgment from the master. The remaining
(1) The value of A0 is determined by the A0 pin.
(2) When INC is set to '0', the address pointer remains unchanged after a read.
(3) Bits P[4:0] point to the register to be written.
Figure 30. Writing a Single Register Timing Diagram
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