Serial RapidIO Subsystem
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
1-25
1.13
Serial RapidIO Subsystem
RapidIO is a high-performance, point-to-point, low-pin-count, packet-switched system-level
interconnect that can be used in a variety of applications as an open standard. The RapidIO
architecture provides a rich variety of features including high data bandwidth, low-latency
capability, and support for high-performance I/O devices, as well as providing message-passing
and software-managed programming models. The Serial RapidIO subsystem consists of a Serial
RapidIO controller and a RapidIO Message Unit (RMU). The MSC8144E device can either
connect directly to a host or to a Serial RapidIO switch. Each port in the switch is point-to-point
connected to the MSC8144E device through a serial RapidIO link. This link typically carries
packets in both directions. Packets ready for processing are transported from the host to the
MSC8144E, and the processed packets are transported from the MSC8144E back to the host.
1.13.1 Serial RapidIO and Host Interactions
The Serial RapidIO controller directs the traffic flow between a host processor and the
MSC8144E device through the RMU. The host and the MSC8144E communicate as follows:
The host may send messages to the destination MSC8144E device, which are sent back to
the host after processing along with a short doorbell interrupt to indicate that the packets
have been processed.
Messages eliminate the latency of read accesses. The host writes to the MSC8144E and
the MSC8144E writes to the host. In addition, messages can be used in applications where
the host does not know the internal memory structure of the target DSP.
The host may directly access the data in the MSC8144E memory for both reads and
writes. It handshakes with the software running on a DSP core through a ring of
descriptors in MSC8144E memory.
The host may access the data in MSC8144E memory for both reads and writes, but instead
of maintaining a ring of descriptors in the MSC8144E memory, it uses buffer descriptors
(BDs) that are messaged from the DSP core to the host.
The host may put all the data buffers into its memory and have the MSC8144E access the
data.
Any initiator on the RapidIO system can access any internal memory space as well as the
DDR SDRAM using NREAD, NWRITE, MESSAGE, and DOORBELLS. In addition, it
can configure the RapidIO messaging and configuration unit using MAINTENANCE
packets.
In the receive path, the following steps occur:
1.
The clock is recovered using a dedicated PLL.
2.
The data is deserialized, 8b/10b decoded, checked for the correct CRC, and passed to
the higher-level protocol logic.
Содержание MSC8144E
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