Shelf Manager ACB-VI
Master-Only I²C Bus
12
R1.2, March 2018
7 Master-Only I²C Bus
The ACB-VI carrier board has a number of onboard I²C devices connected to the local I²C bus.
These devices are:
• PCA9554: reads the hardware address at the backplane connector
• PCA9555: monitors the presence signals from the PEMs, SAP, Air Filter, Fan Trays and the
presence of the input voltages and fuses.
• ADT7490: monitor voltages, monitor/controls the Fan Trays
• LM75: on-board temperature
• SEEPROM: Shelf Manager FRU information
• PCA9543: This 2-channel switch divides the I²C-bus 3 into 2 channels to:
- the SAP (Channel 0)
- the PEMs (Channel 4)
The ’Active’ signal of the ShMM-700R is used to enable the LTC4300, so that only the active
Shelf Manager has access to the Shelf I²C-bus devices.
Figure 10: Master-Only I2C-bus
ShMM-700
I2C0
I2C1
I2C2
I2C3
I2C4 (local)
LTC4300A-1
LTC4300A-1
LTC4300A-1
LTC4300A-1
Bac
k
p
la
n
e
LM75
SEEPROM
LTC4300A-1
Active signal
CH1
CH2
CH3
CH4
CH0
PCA9555
ADT7490
To CDM 1
To CDM 2
To FT
To
PEM,
PSUs
To SAP
ID
TQS
3
VH3
84P
A
G
3.3 V
3.3 V
3.3 V
3.3 V
3.3 V
PCA95
43
0x25
PCA9554
0x23
0x57
0x4F
0x70
0x2C
ADT7490
0x2D
ADT7490
0x2E
3.3 V
3.3 V