Technical Description
3.1.2 PCI Bus
The Peripheral Component Interconnect (PCI) bus is a high bandwidth
multiplexed address/data bus used for control and supervision. Its main use is
for communication between the NPU software and other plug-in units’ software
and functional blocks
3.1.3 SPI Bus
The Serial Peripheral Interface (SPI) is a low speed synchronous serial
interface bus used for:
• Unit status control and LED indication
• Board Removal (BR) button used for unit replacement
• Inventory data
• Temperature and power supervision
• User I/O communication
• Reset of control and traffic logic
3.1.4 Power Bus
The external power supply is connected to a PFU. The internal power supply is
distributed via the Power bus to the other plug-in units. When using two PFUs
in a subrack, the bus is redundant.
3.1.5 BPI Bus
The Board Pair Interconnect (BPI) bus is used for communication between two
plug-in units in a protected (1+1) configuration, for example when using two
LTU 155 units in a Multiplexer Section Protection (MSP)1+1 configuration.
It also interconnects groups of four plug-in units, enabling board protection
schemes including three and four plug-in units.
3.1.6 High Speed Bus
The High Speed Bus joins services to services (for example Ethernet over
VCs dropped by ADM) and services to line interfaces (for example Ethernet
over modem), see Figure 6 on page 9. The high speed bus has dedicated
Point-to-Point connections from the NPU3 B to other PIUs.
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