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ADM1023 Datasheet(PDF) 13 Page - ON Semiconductor

Part No. ADM1023
Description  ACPI‐Compliant, High Accuracy Microprocessor System Temperature Monitor
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Maker  ONSEMI [ON Semiconductor]
Homepage  http://www.onsemi.com
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ADM1023 Datasheet(HTML) 13 Page - ON Semiconductor

 
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ADM1023
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Figure 17. Reading Data from a Previously Selected Register
SCLK
SDATA
D7
D6
D5
D4
D3
D2
D1
D0
NO ACK.
BY MASTER
START BY
MASTER
9
1
ACK. BY
ADM1023
9
STOP BY
MASTER
A6
A5
A4
A3
A2
A1
A0
1
FRAME 1
SERIAL BUS ADDRESS BYTE
FRAME 2
DATA BYTE FROM ADM1023
R/W
Any number of bytes of data may be transferred over the
serial bus in one operation, but it is not possible to mix read
and write in one operation because the type of operation is
determined at the beginning and cannot subsequently be
changed without starting a new operation.
For the ADM1023, write operations contain either one or
two bytes, while read operations contain one byte and
perform the following functions:
To write data to one of the device data registers or read
data from it, the address pointer register must be set so that
the correct data register is addressed. Data can then be
written into that register or read from it. The first byte of a
write operation always contains a valid address that is stored
in the address pointer register. If data is to be written to the
device, the write operation contains a second data byte that
is written to the register selected by the address pointer
register.
This is illustrated in Figure 15. The device address is sent
over the bus followed by R/W set to 0. This is followed by
two data bytes. The first data byte is the address of the
internal data register to be written to, which is stored in the
address pointer register. The second data byte is the data to
be written to the internal data register.
When reading data from a register, there are two
possibilities:
1. If the ADM1023’s address pointer register value is
unknown or not the desired value, it is necessary
to set it to the correct value before data can be read
from the desired data register. This is done by
performing a write to the ADM1023 as before, but
only the data byte containing the register read
address is sent, as data is not to be written to the
register. This is shown in Figure 16.
A read operation is then performed consisting of
the serial bus address, R/W bit set to 1, followed
by the data byte read from the data register. This is
shown in Figure 17.
2. If the address pointer register is known to be at the
desired address already, data can be read from the
corresponding data register without first writing to
the address pointer register.
NOTES:
It is possible to read a data byte from a data register
without first writing to the address pointer register.
However, it is not possible to write data to a register
without writing to the address pointer register even if
the address pointer register is already at the correct
value. This is because the first data byte of a write is
always written to the address pointer register.
Do not forget that ADM1023 registers have different
addresses for read and write operations. The write
address of a register must be written to the address
pointer if data is to be written to that register, but it is
not possible to read data from that address. The read
address of a register must be written to the address
pointer before data can be read from that register.
ALERT Output
The ALERT output goes low whenever an out-of-limit
measurement is detected or if the remote temperature sensor
is open-circuit. It is an open drain and requires a 10 k
W
pull-up to VDD. Several ALERT outputs can be
wire-AND’ed together, so that the common line goes low if
one or more of the ALERT outputs goes low.
The ALERT output can be used as an interrupt signal to a
processor, or it may be used as an SMBALERT. Slave
devices on the SMBus normally cannot signal to the master
that they want to talk, but the SMBALERT function allows
them to do so.
One or more ALERT outputs are 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 18 occurs.
Figure 18. Use of SMBALERT
MASTER
RECEIVES
SMBALERT
MASTER SENDS
ARA AND READ
COMMAND
DEVICE SENDS
ITS ADDRESS
NO
ACK
START
ALERT RESPONSE
ADDRESS
RD ACK
DEVICE
ADDRESS
STOP
SMBALERT Process
1. SMBALERT pulled low.
2. Master 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 device whose ALERT output is low responds
to the ARA and the master reads its device


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