Serial Bus Interface; Changes To Comparisons Between The Adt7467 And Adt7476 Section - Analog Devices ADT7473 Manual

ADT7473/ADT7473-1

SERIAL BUS INTERFACE

On PCs and servers, control of the ADT7473/ADT7473-1 is
carried out using the SMBus. The ADT7473/ADT7473-1 is
connected to this bus as a slave device, under the control of a
master controller, which is usually (but not necessarily) the ICH.
The ADT7473 has a fixed 7-bit serial bus address of 0101110 or
0x2E. The read/write bit must be added to get the 8-bit address
(01011100 or 0x5C). When the ADT7473-1 is powered up with
Pin 8 (PWM3/ ADDREN ) high, the ADT7473-1 has a default
SMBus address of 0101110 or 0x2E. If more than one
ADT7473-1 is used in a system, each ADT7473-1 is placed in
ADDR SELECT mode by strapping Pin 8 low on power-up. The
logic state of Pin 4 then determines the device's SMBus address.
The logic of these pins is sampled on power-up.
The device address is sampled on power-up and latched on
the first valid SMBus transaction, more precisely on the low-to-
high transition at the beginning of the eighth SCL pulse, when
the serial bus address byte matches the selected slave address.
The selected slave address is chosen using the ADDREN pin/
ADDR SELECT pin. Any attempted change in the address
has no effect after this.
Table 7. Hardwiring the ADT7473-1 SMBus Device Address
Pin 8 State Pin 4
0 Low (10 kΩ to GND)
0 High (10 kΩ pull-up)
1 Don't care
FRONT
CHASSIS
FAN
REAR
CHASSIS
FAN
AMBIENT
TEMPERATURE
Figure 14. ADT7473 Configuration
Address
0101100 (0x2C)
0101101 (0x2D)
0101110 (0x2E)
ADT7473
PWM1
TACH2
TACH1
PWM3
D2+
TACH3
D2–
THERM
PROCHOT
D1+
SDA
D1–
SCL
SMBALERT
GND
Figure 16. SMBus Address = 0x2C (Pin4 = 0)
Figure 17. SMBus Address = 0x2D (Pin 4 = 1)
Rev. C | Page 10 of 72
CPU FAN
CPU
ICH
V
ADT7473-1
CC
4
ADDR SELECT
10kΩ
8
PWM3/ADDREN
ADDRESS = 0x2E
Figure 15. Default SMBus Address = 0x2E
ADT7473-1
10kΩ
4
ADDR SELECT
8
PWM3/ADDREN
ADDRESS = 0x2C
V
CC
ADT7473-1
10kΩ
4
ADDR SELECT
8
PWM3/ADDREN
ADDRESS = 0x2D