ADM1191 Просмотр технического описания (PDF) - Analog Devices
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ADM1191 Datasheet PDF : 16 Pages
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WRITE AND READ OPERATIONS
The I2C specification defines several protocols for different
types of read and write operations. The operations used in the
ADM1191 are discussed in the sections that follow. Table 6
shows the abbreviations used in the command diagrams.
Table 6. I2C Abbreviations
Abbreviation
S
P
R
W
A
N
Condition
Start
Stop
Read
Write
Acknowledge
No acknowledge
QUICK COMMAND
The quick command operation allows the master to check if the
slave is present on the bus, as follows:
1. The master device asserts a start condition on SDA.
2. The master sends the 7-bit slave address, followed by the
write bit (low).
3. The addressed slave device asserts an acknowledge on SDA.
1
2
3
S
SLAVE
ADDRESS
WA
Figure 19. Quick Command
ADM1191
WRITE COMMAND BYTE
In the write command byte operation, the master device sends
a command byte to the slave device, as follows:
1. The master device asserts a start condition on SDA.
2. The master sends the 7-bit slave address, followed by the
write bit (low).
3. The addressed slave device asserts an acknowledge on SDA.
4. The master sends the command byte. The command byte
is identified by an MSB = 0. An MSB =1 indicates an
extended register write (see the Write Extended Byte
section).
5. The slave asserts an acknowledge on SDA.
6. The master asserts a stop condition on SDA to end the
transaction.
1
2
3
4
56
S
SLAVE
ADDRESS
WA
COMMAND
BYTE
A
P
Figure 20. Write Command Byte
The seven LSBs of the command byte are used to configure and
control the ADM1191. Table 7 provides details of the function
of each bit.
Table 7. Command Byte Operations
Bit Default Name
Function
C0 0
V_CONT
Set to convert voltage continuously. If readback is attempted before the first conversion is complete,
the ADM1191 asserts an acknowledge and returns all 0s in the returned data.
C1 0
V_ONCE
Set to convert voltage once. Self-clears. I2C asserts a no acknowledge on attempted reads until the ADC
conversion is complete.
C2 0
I_CONT
Set to convert voltage continuously. If readback is attempted before the first conversion is complete,
the ADM1191 asserts an acknowledge and returns all 0s in the returned data.
C3 0
I_ONCE
Set to convert current once. Self-clears. I2C asserts a no acknowledge on attempted reads until the ADC
conversion is complete.
C4 0
VRANGE
Selects different internal attenuation resistor networks for voltage readback. A 0 in C4 selects a 14:1 voltage
divider. A 1 in C4 selects a 7:2 voltage divider. With an ADC full scale of 1.902 V, the voltage at the VCC pin for
an ADC full-scale result is 26.52 V for VRANGE = 0 and 6.65 V for VRANGE = 1.
C5 0
N/A
Unused,
C6 0
STATUS_RD Status Read. When this bit is set, the data byte read back from the ADM1191 is the STATUS byte. It contains
the status of the device alerts. See Table 15 for full details of the STATUS byte.
Rev. 0 | Page 11 of 16
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