AEROFLEX GAISLER
22
RT-SPW-ROUTER
Copyright Aeroflex Gaisler AB
June 2012, Version 1.2
The AMBA interface is divided into the AHB master interface and the APB interface. The DMA
engines have FIFO interfaces to the router switch matrix. These FIFOs are used to transfer N-Chars
between the AMBA bus and the other ports in the router.
The RMAP target handles incoming packets which are determined to be RMAP commands instead of
the receiver DMA engine. The RMAP command is decoded and if it is valid, the operation is per-
formed on the AHB bus. If a reply was requested it is automatically transmitted back to the source by
the RMAP transmitter.
3.5.2.1
Protocol support
The AMBA port only accepts packets with a valid destination address in the first received byte. Pack-
ets with address mismatch will be silently discarded (except in promiscuous mode which is covered in
section 3.5.3.10).
The second byte is sometimes interpreted as a protocol ID a described hereafter. The RMAP protocol
(ID=0x1) is the only protocol handled separately in hardware while other packets are stored to a DMA
channel. If the RMAP target is present and enabled all RMAP commands will be processed, executed
and replied automatically in hardware. Otherwise RMAP commands are stored to a DMA channel in
the same way as other packets. RMAP replies are always stored to a DMA channel. More information
on the RMAP protocol support is found in section 3.5.5 (note that this RMAP target is different from
the one in the configuration port). When the RMAP target is not present or disabled, there is no need
to include a protocol ID in the packets and the data can start immediately after the address.
All packets arriving with the extended protocol ID (0x00) are stored to a DMA channel. This means
that the hardware RMAP target will not work if the incoming RMAP packets use the extended proto-
col ID. Note also that packets with the reserved extended protocol identifier (ID = 0x000000) are not
ignored by the AMBA port. It is up to the client receiving the packets to ignore them.
When transmitting packets, the address and protocol-ID fields must be included in the buffers from
where data is fetched. They are not automatically added by the AMBA port DMA engine.
Figure 7 shows the packet types accepted by the port. The port also allows reception and transmission
with extended protocol identifiers but without support for RMAP CRC calculations and the RMAP
target.
3.5.2.2
Time interface
The time interface is used for sending Time-codes over the SpaceWire network and consists of a time-
counter register, time-ctrl register, tick-in signal, tick-out signal, tick-in register field and a tick-out
register field. There are also two control register bits which enable the time receiver and transmitter
respectively.
Each Time-code sent from the sent from the port is a concatenation of the time-ctrl and the time-
counter register. There is a timetxen bit which is used to enable Time-code transmissions. It is not
possible to send time-codes if this bit is zero.
Figure 7. The SpaceWire packet types supported by the port.
Addr ProtID
Dn-2
..
D3
D2
D1
D0
Dn-1
EOP
Addr
D0
Dm-2
..
D4
D3
D2
D1
Dm-1
EOP
