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GR716-DS-UM, May 2019, Version 1.29
297
www.cobham.com/gaisler
GR716
33.2
Operation
33.2.1 Overview
The main sub-blocks of the core are the link interface, the RMAP target and the AMBA interface. A
block diagram of the internal structure can be found in figure 48.
The link interface consists of the receiver, transmitter, and the link interface FSM. They handle com-
munication on the SpaceWire network. The PHY block provides a common interface for the receiver
to the four different data recovery schemes and is external to this core. The AMBA interface consists
of the DMA engines, the AHB master interface and the APB interface. The link interface provides
FIFO interfaces to the DMA engines. These FIFOs are used to transfer N-Chars between the AMBA
and SpaceWire domains during reception and transmission.
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.
33.2.2 Protocol support
The core only accepts packets with a valid destination address in the first received byte. Packets with
address mismatch will be silently discarded (except in promiscuous mode, which is covered in section
33.6.10).
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 33.8. When the RMAP target is not present or dis-
abled, 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-
Figure 48.
Block diagram
TRANSMITTER
TXCLK
TRANSMITTER
FSM
LINKINTERFACE
SEND
RMAP
D
S
FSM
FSM
TRANSMITTER
DMA ENGINE
RECEIVER
DMA ENGINE
TRANSMITTER
RMAP
RECEIVER
N-CHAR
FIFO
RECEIVER
AHB FIFO
RECEIVER DATA
PARALLELIZATION
AHB
MASTER INTERFACE
REGISTERS
APB
INTERFACE
RECEIVER1
PHY
D
S
D
DV