5.14.5. Power Supply Field Replacement Unit (FRU)
The power supply shall support electronic access of FRU information over an I2C bus. Five
pins at the power supply connector are allocated for this. They are named SCL, SDA, A1, A0 and
Write protect. SCL is serial clock. SDA is serial data. These two bidirectional signals from the
basic communication lines over the I2C bus. A0and A1 are input address lines to the power
supply. The backplane defines the state of these lines such that the address to the power supply
is unique within the system. The resulting I2C address shall be per table below. The Write
protection pin is to ensure that data will not accidentally overwritten.
The device used for this shall be powered from a 3.3V bias voltage derived from the 5VSB
output . No pull‐up resistors shall be on SCL or SDA inside the power supply.
Figure 56 PSU EEPROM Addressing
5.14.6. PSMC Sensors
Sensors shall be available to the PSMC for monitoring purpose. All Sensors shall continue
to provide real time data as long as the PSMC device is powered. This means in standby and
operation mode, while in standby the main output(s) of the power supply shall read zero Amps
and Volts.
Table 39 PSU PSMC Sensor list
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