ADT7485A
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8
Table 7. 16-BYTE DIB DETAILS
Byte Name Value Description
0 Device
Capabilities
0xc0 Fixed Address
Device
1 Version/Revision 0x10 Meets Version 1 of
SST Specification
2, 3 Vendor ID 00x11d4 Contains Company
ID Number in Little
Endian Format
4, 5 Device ID 0x7485 Contains Device ID
Number in Little
Endian Format
6 Device Interface 0x01 SST Device
7 Function
Interface
0x00 Reserved
8 Reserved 0x00 Reserved
9 Reserved 0x00 Reserved
10 Reserved 0x00 Reserved
11 Reserved 0x00 Reserved
12 Reserved 0x00 Reserved
13 Reserved 0x00 Reserved
14 Revision ID 0x05 Contains Revision ID
15 Client Device
Address
0x48 to
0x4a
Dependent on the
State of Address
Pin
Ping()
The Ping() command verifies if a device is responding at
a particular address. The ADT7485A shows a valid non-zero
FCS in response to the Ping() command when correctly
addressed.
Table 8. PING() COMMAND
Target Address Write Length Read Length FCS
(Not Necessary) 0x00 0x00
ResetDevice()
This command resets the register map and conversion
controller. The reset command can be global or directed at
the client address of the ADT7485A.
Table 9. RESETDEVICE() COMMAND
Target Address
Write
Length
Read
Length
Reset
Command
FCS
Device Address 0x01 0x00 0xf6
GetIntTemp()
The ADT7485A shows the local temperature of the device
in response to the GetIntTemp() command. The data has a
little endian, 16-bit, twos complement format.
GetExtTemp()
Prompted by the GetExtTemp() command, the ADT7485A
shows the temperature of the remote diode in little endian,
16-bit, twos complement format. The ADT7485A shows
0x8000 in response to this command if the external diode is
an open or short circuit.
GetAllTemps()
The ADT7485A shows the local and remote temperatures
in a 4-byte block of data (internal temperature first, followed
by external temperature) in response to a GetAllTemps()
command.
SetExtOffset()
This command sets the offset that the ADT7485A will use
to correct errors in the external diode. The offset is set in little
endian, 16-bit, twos complement format. The maximum
offset is 128C with +0.25C resolution.
GetExtOffset()
This command causes the ADT7485A to show the offset
that it is using to correct errors in the external diode. The
offset value is returned in little endian format, that is, LSB
before MSB.
ADT7485A Response to Unsupported Commands
A full list of command codes supported by the
ADT7485A is given in Table 6. The offset registers
(Command Code 0xe0) are the only registers that the user
can write to. The other defined registers are read only.
Writing to Register Addresses 0x02, 0x09, and 0x15 to 0xdf
shows a valid FSC, but no action is taken by the ADT7485A.
The ADT7485A shows an invalid FSC if the user attempts
to write to the device between Command Codes 0xe2 to
0xee. These registers are reserved for the manufacturer’s use
only, and no data can be written to the device via these
addresses.
Voltage Measurement
The ADT7485A has four external voltage measurement
channels. It can also measure its own supply voltage, V
CC
.
Pins 5 and 8 measure the supplies of the 12 V, 5.0 V,
processor core voltage (V
CCP
), and 2.5 V pins, respectively.
The V
CC
supply voltage measurement is carried out through
the V
CC
pin (Pin 1). The 2.5 V pin can be used to monitor a
chip-set supply voltage in a computer system.
Analog-to-Digital Converter
All analog inputs are multiplexed into the on-chip,
successive approximation, analog-to-digital converter
(ADC). This has a resolution of 10 bits. The basic input
range is 0 V to 2.25 V, but the inputs have built-in
attenuators to allow measurement of 2.5 V, 3.3 V, 5.0 V,
12 V, and the processor core voltage (V
CCP
) without any
external components.
To allow for the tolerance of these supply voltages, the
ADC produces a specific output for each nominal input
voltage and therefore has adequate headroom to cope with
overvoltage. The full-scale voltage that can be recorded for
each channel is shown in Table 10.
