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Transcript
AEROFLEX GAISLER 596 GRIP Each SpaceWire address register has a corresponding mask register. Only bits at an index containing a zero in the corresponding mask register are compared. This way a DMA channel can accept a range of addresses. There is a default address register which is used for address checking in all implemented DMA channels that do not have separate addressing enabled and for RMAP commands in the RMAP target. With separate addressing enabled the DMA channels’ own address/mask register pair is used instead. If an RMAP command is received it is only handled by the target if the default address register (including mask) matches the received address. Otherwise the packet will be stored to a DMA channel if one or more of them has a matching address. If the address does not match neither the default address nor one of the DMA channels’ separate register, the packet is still handled by the RMAP target if enabled since it has to return the invalid address error code. The packet is only discarded (up to and including the next EOP/EEP) if an address match cannot be found and the RMAP target is disabled. Packets, other than RMAP commands, that do not match neither the default address register nor the DMA channels’ address register will be discarded. Figure 170 shows a flowchart of packet reception. At least 2 non EOP/EEP N-Chars needs to be received for a packet to be stored to the DMA channel unless the promiscuous mode is enabled in which case 1 N-Char is enough. If it is an RMAP packet with hardware RMAP enabled 3 N-Chars are needed since the command byte determines where the packet is processed. Packets smaller than these sizes are discarded.
