Atmel SpaceWire Router SpW-10X - Manual (Page 59)

Ref.: UoD_SpW-10X_
UserManual
Issue: 3.4
SpW-10X
SpaceWire Router
User Manual Date: 11 th
July 2008
Preliminary
59
Length one 32 bit register location.
Header
CRC
The header CRC is the eight bit CRC code used to detect errors in the
command packet. The CRC code is checked before the command is
executed
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In Figure 7-4 the format of the reply to a read single address command is illustrated. The first byte sent
by the SpaceWire router configuration logic is the port address followed by the destination logical
address. Fields which are depicted in bold text are expected values. Fields which are shaded are
optional. Note that the reply is always sent out of the same port as the command was received on.
The Source Path Address should not include the output port of the router being commanded as the
reply will be automatically sent out of the same port that the command arrived on. See section 7.6.8.
Source Path Address
Source Logical Address
Protocol Identifier
01h
Packet Type, Command,
Source Path Addr Len
Status
Destination Logical Address
FEh
Transaction Identifier (MS) Transaction Identifier (LS) Reserved = 0
Data Length (MS)
00h
Data Length
00h
Data Length (LS)
04h
Header CRC
Data (Word 0 MSB) Data Data Data (Word 0 LSB)
Source Path Address Source Path Address
Data CRC EOP
First byte transmitted
Last byte transmitted
0 0 0 0 1 0
Bits in Packet Type / Command / Source Address Path Length Byte
MSB
Packet Type Command
Source Path
Address Length
Source Path
Address Length
LSB
Source Path Address Length
Figure 7-4 Read Single Address Reply Packet Format
Table 7-7 Read Single Address Reply Packet Fields
Field Description Bytes
Source
Path
Address
Optional source path addresses specified in the command packet. If no source
path addresses are specified then the first byte will be the source logical
address.
>=0
Source
Logical
Address
The source logical address specified in the command packet. If source path
addresses are not used then the source logical address is the address of the
return packet.
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