IEEE 1394-2008 pdf download IEEE Standard for a High-Performance Serial Bus
Whether or not spced is explicitly signaled, TX DATA PREFIX shall be signaled by any transmitting portfor at least the minimum time shown before clocked data are transmitted. For improved interoperability withlegacy devices, TX DATA PREFIX should be signaled by the originating port(s) for a minimum of 180 nsprior to clocked data. Speed signaling occurs concurrently with data prefix but may commence up to 20 nsbefore the start of data prefix. This is difficult to show graphically and is represented by a negative value forARB SPEED SIGNAL START. Once speed signaling is initiated by a transmitting port, it shall becontinued for SPEED SIGNAL LENGTH time. Speed signaling shall complete no less thanDATA PREFIX HOLD time before the start of clocked data.
ata prefix and speed signaling between two concatenated packets is similar to that for the first packet butthe speed signal is shifted later into the data prefix time as illustrated by Figure 9-1l.
Arbitration orClocked data
TX DATA PREFIX
Speed signal
CONCATENTATION PREFIX TIME-
DATA PREFIX HOLD
SPEED SIGNAL LENGTH
– MIN PACKET_SEPARATION
Figure 9-11-Concatenated packet transmission
Originating ports shall guarantee MIN PACKET SEPARATION time between the clocked data of any twoconcatenated packets. Clock frequency and phase diferences may cause a smaller separation at repeatingports. but in no case shall the minimum packet separation be less than the sum ofCONCATENATION PREFIX TIME,SPEED SIGNAL LENGTH,a DATA PREFIX HOLD.AACrthe end of clocked data for the previous packet, a transmitting port shall guarantee a delay ofCONCATENATION PREFIX TIME before signaling the speed of the next packet. The requirements forSPEED SIGNAL LENGTH and DATA PREFIX HOLD are the same as for start of packet transmission.
IEEE 1394-2008 pdf download
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