Service manual

System Overview 1-33
Figure 1–15 is a block diagram of the hierarchical switch power manager (HPM)
module. The HPM is responsible for monitoring environmental sensors on the
H-switch and reporting unsafe conditions. The HPM is powered by Vaux which
is converted to +5V and +3.3V on the module.
The HPM monitors two clock signals and several power supply signals that
must be good and remain good during power-on and normal operation. If any
fail, the H-switch is turned off.
The HPM performs a reset, initialize, and functional self-test for the H-switch.
If these functions pass, the HPM enters a stand-by state; if they fail, the HPM
remains in the initialize state, the reset/initialize LED remains on, and the CSB
remains operational so that failure data can be reported to the SCM.
The microprocessor operation is controlled by firmware stored in flash memory
on the HPM, and receives commands from the SCM through the console serial
bus (CSB) interface. The flash memory contains the HPM firmware code and a
sector with a fail-safe loader (FSL). Updating of the flash program image is
done by LFU or by downloading the data over the CSB using the SCM update
command.
The HPM has one I
2
C bus and is shared between devices mounted on the H-
switch, and on the HPM module itself. The HPM module also contains a 256x8-
bit EEPROM, and one LM80 device for monitoring DC voltages and temper-
ature on the H-switch.
For a description of the HPM module, see Section 1.20.