GR740-UM-DS, Nov 2017, Version 1.7
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GR740
35
SpaceWire Debug Link
35.1
Overview
The SpaceWire core provides an interface between the AHB bus and a SpaceWire network. It imple-
ments the SpaceWire standard [SPW] with the protocol identification extension [SPWID]. The
Remote Memory Access Protocol (RMAP) target implements [RMAP].
The SpaceWire interface is configured through a set of registers accessed through an APB interface.
Data is transferred through DMA channels using an AHB master interface.
The GRSPW2 SpaceWire core is located on the Debug AHB bus and has an RMAP target that is
enabled after system reset. The core APB interface is also available on the Debug AHB bus but cannot
be accessed by the processors since the bridge connecting the Debug AHB bus to the Processor AHB
bus is uni-directional. The core on the Debug AHB bus thus provides a SpaceWire debug link that can
be used to access all parts of the system. The system’s main SpaceWire links are provided through the
SpaceWire router, see section 13.
The SpaceWire debug interface will, together with all other cores on the Debug AHB bus, be gated off
when the Debug AHB bus is disabled via the external DSU_EN signal.
35.2
Operation
35.2.1 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 46.
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-
Figure 46.
Block diagram
TRANSMITTER
TXCLK
TRANSMITTER
FSM
LINKINTERFACE
SEND
RMAP
D(1:0)
S(1:0)
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
D0
S0
RECEIVER0
PHY
D
DV