Datasheet

ADT7411
Rev. B | Page 34 of 36
D7
D6
D5
D4
D3
D2
D1
X
X
X
X
X
X
X
D0
X
CS
SCLK
DIN
DOUT
START
READ COMMAND
181
8
X
XX
X
X
X
X
D6
D5
D4
D3
D2
D1
D0
XD7
CS (CONTINUED)
SCLK (CONTINUED)
DIN (CONTINUED)
DOUT (CONTINUED)
STOP
DATA BYTE 2
DATA BYTE 1
X
X
X
X
X
X
X
X
1
8
D7
D6 D5 D4 D3
D2
D1
D0
02882-039
Figure 40. SPI—Reading Two Bytes of Data from Two Sequential Registers
CS
SPI READ OPERATION WRITE OPERATION
02882-040
Figure 41. SPI—Correct Use of
CS
During SPI Communications
The INT/
INT
output can operate as an
SMBALERT
function.
Slave devices on the SMBus can normally not signal to the
master that they want to talk, but the
SMBALERT
function
allows them to do so.
SMBALERT
is used in conjunction with
the SMBus general call address.
One or more INT/
INT
outputs can be connected to a common
SMBALERT
line connected to the master. When the
SMBALERT
line is pulled low by one of the devices, the
procedure shown in Figure 42 occurs.
MASTER
RECEIVES
SMBALERT
START
ALERT RESPONSE
ADDRESS
RD ACK DEVICE ADDRESS
MASTER SENDS
ARA AND READ
COMMAND
DEVICE SENDS
ITS ADDRESS
NO
ACK
STOP
02882-041
Figure 42. INT/
INT
Responds to
SMBALERT
ARA
1.
SMBALERT
is pulled low.
2. M
aster initiates a read operation and sends the alert
response address (ARA = 0001 100). This is a general call
address that must not be used as a specific device address.
3. The de
vice whose INT/
INT
output is low responds to the
alert response address and the master reads its device
address. As the device address is seven bits long, an LSB of
1 is added. The address of the device is now known and it
can be interrogated in the usual way.
4. I
f more than one device’s INT/
INT
output is low, the one
with the lowest device address has priority, in accordance
with normal SMBus specifications.
5. On
ce the ADT7411 responds to the alert response address,
it resets its INT/
INT
output, provided that the condition
that caused the out-of-limit event no longer exists and the
status register associated with the out-of-limit event is read.
If the
SMBALERT
line remains low, the master sends the
ARA again. It continues to do this until all devices whose
SMBALERT
outputs were low have responded.
MASTER
RECEIVES
SMBALERT
START
ALERT RESPONSE
ADDRESS
RD ACK
DEVICE
ADDRESS
MASTER SENDS
ARA AND READ
COMMAND
DEVICE SENDS
ITS ADDRESS
DEVICE ACK
ACK PEC
NO
ACK
STOP
MASTER
ACK
MASTER
NACK
DEVICE SENDS
ITS PEC DATA
02882-042
Figure 43. INT/
INT
Responds to
SMBALERT
ARA with Packet Error Checking