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The following procedure can be used to restart a link following an error (routing is assumed disabled):
1)
Disconnect is detected (cause: error)
2)
SMCS332SpW enters "exchange of silence"
if the corresponding interrupt mask bit is enabled, the SMCS332SpW HINTR* signal will be asserted.
3)
The transmit section is reset by the SMCS332SpW after an error has occurred. Any currently on-going
transmit transfer via COMI is stopped.
The user can decide to read the receive-FIFO (if not empty) and then to reset the receive section or to reset
the receive section immediately without reading the receive-FIFO.
Resetting the receive section is done by setting and clearing bit1 in register CHx_CNTRL2.
If the protocol mode is used the protocol unit should be reset by setting and clearing bit2 in register
CHx_CNTRL2.
4)
If the auto start bit (bit2, CHx_DSM_CMDR) is set, the link will start automatically after the "protocol of
silence", otherwise the user has to start the link by setting bit1 in CHx_DSM_CMDR.
The configuration registers are not affected by the disconnect error.
5)
New transmit and receive transfers can be started.
3.5
SpaceWire state on start up
After power-on all LinkData and LinkStrobe signals are low, without clocks. Following power-on reset an initialization
sequence sets the speed of the link clock. The DS-Links are initially inactive. They are configured and started by
configuration writes. Their status can be determined by configuration reads.
Each link must be explicitly started by writing to the Start Transmit Node bit in its CHx_DSM_CMDR register. When a
SpaceWire link is started up it transmits NULL's. Data may not be transferred over the link until the receiving link has sent a
FCT, which it will do as soon as it has been started. In remote mode (control by link) however, the SMCS332SpW will send
characters as soon as it receives a NULL on one of the three links, the control link.
The receiving link receives and correctly decodes the characters. However, only when the receiving link has been explicitly
started by writing across the (internal) configuration bus can it send characters back. NULL's are then sent until data is
required.
A start up sequence between SpaceWire devices cannot be defined in general. The start up depends heavily on the system
(user) requirements and consequently on the procedure defined at system level to initialize the system or to recover from an
error.
No master-slave arrangement is necessary. The SpaceWire links are "hot plug" able., which means SpaceWire links can be
connected together at any time.
3.6
Link connections
SpaceWire links are TTL compatible and intended to be used in electrically quiet environments, between devices on a single
printed circuit board or between two boards via a backplane. Direct connection may be made between devices separated by a
distance of less than 200 millimeters. For longer distances a matched 100 ohm transmission line should be used together with
differential link transceivers (LVDS). The inputs and outputs have been designed to have minimum skew at the 1.5 V TTL
threshold. Buffers may be used for very long transmissions. If so, their overall propagation delay should be stable within the
skew tolerance of the link, although the absolute value of the delay is immaterial.
For more information see [AD1].
SMCS332SpW
User Manual
– All Rights Reserved – Copyright per DIN 34 –
EADS Astrium GmbH, ASE2
Doc No: SMCS_ASTD_UM_100
Issue:
1.4
Updated: 9-Sep-2006
Page:
17 of 131
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