Advertisement
6.0 PORT ADDRESSING
6.1 Path Addressing
Path Addressing is defined as a series of one or more characters at the start of the packet that define the route, or path,
that the packet should take across a SpaceWire network. The destination address is specified as a sequence of router
output port numbers used to route the packet across the network. The drawback is that the destination address can
become relatively large if several routing switches have to be traversed. Path Addressing is used for configuration of
the router. The routers look up tables does not have to be configured when path addressing is being used.
A packet with header 0x01 will be routed to Router port 1, a 0x02 header will be routed to port 2, 0x03 will be routed
to port 3, and so on. Please see the following table for a list of valid path addresses.
6.2
Logical Addressing
The router can be configured to use Logical addressing by using path addressing to configure the look up tables.
Logical Addressing contains a character at the start of a packet, which identifies a look up table location and then
selects the destination for the packet. Each destination address has a unique number or logical address associated with
it. These numbers can be assigned arbitrarily to nodes provided.
To access logical routing the user must configure the look-up tables. The looks up tables in the 4-Port router have
even parity. Valid look up table address locations are 0x0020 to 0x00F. If a portion of the look up table addressing
space is not going to be used, it is preferred if the user sets used addressed to 0x00.
6.3 Regional Logical Addressing
This addressing scheme is the same as Logical Addressing except for the fact that header delete is used. When using
Regional Logical Addressing the look up tables contains the information on which headers to keep and or delete.
6.4 Group Adaptive
The last SpaceWire addressing scheme is group adaptive. When Group adaptive routing is used, packets can be
routed to a requested destination through different network paths. Group adaptive routing can be set up for two paths.
To utilize group adaptive routing, the user must configure Group adaptive bits in look-up table. Bits 5 through 9 are
group adaptive address, and Bit 11 must be set to 0x01 to enable group adaptive routing. To use Logical or Group
Adaptive addressing the router must be configured to set up these functions
6.5 Look Up Table Data Format
The lookup tables on the router are organized into 16-bits and are organized as shown below.
6.5.1 Primary Logical Address Bits
The five LSB bits [4:0] are the Primary Logical Address bits and are for selecting ports 1 through 4
regardless of whether Group Adaptive has been enabled or not. When Group Adaptive has been enabled, the
router looks at the port address specified by these bits first and if that port is busy, then looks at the port
specified by the Group Adaptive Address Bits.
Table 21. Path Address Byte Memory Map
Address Byte (HEX)
0x01
0x02
0x03
0x04
0x05
Figure 13. Look-up Table Format
Port
Path Address for Port 1
Path Address for Port 2
Path Address for Port 3
Path Address for Port 4
Path Address for HOST port
25
Advertisement
