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In this first example, there is a synchronisation to the external clock at the start of each packet:
@4 (/w s) 5*{ hold 0 0 0 0 eop }
Tx:@4 /* /w s */ HOLD #00 #00 #00 #00 EOP
Tx:@4 HOLD #00 #00 #00 #00 EOP
Tx:@4 HOLD #00 #00 #00 #00 EOP
Tx:@4 HOLD #00 #00 #00 #00 EOP
Tx:@4 HOLD #00 #00 #00 #00 EOP
Rx:@4 /*208:22:48:09.000 000 538 9s [-6]*/ #00 #00 #00 #00 EOP
Rx:@4 /*208:22:48:10.000 000 566 9s [-6]*/ #00 #00 #00 #00 EOP
Rx:@4 /*208:22:48:11.000 000 558 9s [-6]*/ #00 #00 #00 #00 EOP
Rx:@4 /*208:22:48:12.000 000 497 6s [-6]*/ #00 #00 #00 #00 EOP
Rx:@4 /*208:22:48:13.000 000 569 6s [-6]*/ #00 #00 #00 #00 EOP
Following the rising edge of the clock on the SMA input connector, there is a delay before transmission onto
SpaceWire of the byte following the HOLD character; at 100Mb/s, this is approximately 500 ns.
In this second example, there is a synchronisation on each byte of a packet (and its EOP):
@4 (/w sme) hold 0 hold 0 hold 0 hold 0 hold eop
Tx:@4 /* /w sme */ HOLD #00 HOLD #00 HOLD #00 HOLD #00 HOLD EOP
Rx:@4 /*208:22:47:44.000 000 522 9s [-6]*/ #00
Rx:@4 /*208:22:47:45.000 000 573 6s [-6]*/ #00
Rx:@4 /*208:22:47:46.000 000 549 6s [-6]*/ #00
Rx:@4 /*208:22:47:47.000 000 597 6s [-6]*/ #00
Rx:@4 /*208:22:47:48.000 000 497 6s [-6]*/ EOP
14
Option OD and OE – Output Disable and Output Enable
From DSI firmware v21, the DSI provides the capability to disable all of its SpaceWire output signals in response to
an input logic signal on one of its rear-panel SMA connector pairs. In conjunction with monitoring hardware or
software, that detects anomalies within a wider EGSE, these options can be used to provide further protection to
delicate or valuable SpaceWire hardware.
The Output Disable option (OD) responds to a high-level input signal on SMA connector pair J3-J4, and tri-states
the SpaceWire ports. When J3-J4 is not driven, the DSI behaves as it normally would without this option. With the
OD option, the existing J3-J4 functions remain unchanged; e.g. the DSI can still trigger an event waveform capture
when this signal is raised. The drawback to the Output Disable configuration is that a broken or disconnected
cable will not be detected.
The Output Enable option (OE) only enables the SpaceWire outputs when a high-level input signal is present on
SMA connector pair J3-J4, making it fail safe in the face of a broken enable signal connection. The drawback to
this option is that the DSI will appear inert unless J3-J4 is driven high, which is a non-standard behaviour. With the
OE option, the existing J3-J4 functions may be used with reversed polarity; the DSI triggers an event waveform
capture when the input signal falls.
The OD and OE options indicate “-3S-” on the DSI unit’s front panel display when its SpaceWire outputs are tri-
stated. This is shown in Figure 14-1.
Содержание Diagnostic SpaceWire Interface
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