Network Interrupts; Redundant Transfer Mode Of Operation - GE PCIE-5565PIORC* Hardware Reference Manual

2.6 Network Interrupts

2.7 Redundant Transfer Mode of Operation

The RFM‐5565 is capable of passing interrupt packets, as well as data packets,
over the network. The network interrupt packets can be directed to a specific node
or broadcast globally to all other nodes on the network. Each network interrupt
packet contains the sender's node ID, the destination node ID, the interrupt type
and 32 bits of user defined data.
The types of network interrupts include four general purpose interrupts and a
reset node request interrupt. Node specific interrupts are sent by configuring
three RFM Control and Status registers. Each receiving node evaluates the
interrupt packets as they pass through. If a general purpose interrupt is directed
to that node, then the sender's node ID is stored in the appropriate Sender ID
FIFO (one of four). Each Sender ID FIFO is 127 locations deep. The accompanying
data will be stored in a companion 127 locations deep data FIFO.
If enabled through the LISR, LIER and INTCSR registers, any of the network
interrupts can also generate a host PCI interrupt at each receiving node.
The reset node request interrupt is not stored in a FIFO like the four general
purpose interrupts. Furthermore, it does not cause an immediate reset of the
board. Instead, it sets a bit in the LISR register, which will result in a PCI
interrupt if enabled. The actual board reset should be performed by the host
system in an orderly fashion. However, the user application could use this
network interrupt for any purpose.
The RFM‐5565 is capable of operating in a redundant transfer mode. The board is
configured for redundant mode when switch S1 position 1 is in the ON position.
In the redundant transfer mode, each packet transfers twice, regardless of the
packet size. The receiving circuitry of each node on the network evaluates each of
the redundant transfers. If no errors are detected in the first transfer, it is used to
update the onboard memory and the second transfer is discarded. However, if the
first transfer contains an error, the second transfer is used to update the onboard
memory provided it has no transmission errors. If errors are detected in both
transfers, the transfers will not be used and the data is completely removed from
the network.
Redundant transfer mode reduces the chance that any data is dropped from the
network. However, the redundant transfer mode also reduces the network data
transfer rate. The single Dword (Double‐word = 4 bytes) transfer rate drops from
the non‐redundant rate of 43 MByte/s to approximately 20 MByte/s. The
16 Dword (64 byte) transfer rate drops from the non‐redundant rate of
170 MByte/s to the redundant rate of 85 MByte/s.
Theory of Operation 27