REAL-TIME SYSTEMS II Real-Time Networking WorldFIP ... - EPFL

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Cyclic message transfers Cyclic message transfers (2) Real-Time Networks – WorldFIP 29 • use one or more variable identifiers configured for this type of transfer. The same Ids may be used for buffer transfer. • a file (queue F_MSGcyc) is associated to each identifier • messages stored in the F_MSGcyc queue associated to the identifier indicated in the request • request served in the periodic window (even if no msg pending) • transfer is performed with or without ack ©2010, J.-D. Decotignie SOURCE L_MESSAGE_ACK. request L_SENT.indication L_MESSAGE_ACK. confirmation Real-Time Networks – WorldFIP 30 DLL ID=n B_DAT prod MSG ID=n F_MSG cyc BUS ARBITER ID_DAT n RP_DAT ID_MSG n RP_MSG_ACK RP_ACK RP_FIN DLL F_MSG reçu DESTINATION L_MESSAGE_ACK. indication ©2010, J.-D. Decotignie Aperiodic message transfers Aperiodic message transfer • no identifier is indicated in the request Real-Time Networks – WorldFIP 31 • identifier is chosen by the DLL • it must be configured for this type of service • it must correspond to a variable produced by the given station(source of message) • it must be already associated to a message in the queue • the request is signaled to the bus arbiter in the response to an ID_DAT frame with the selected identifier • association with the identifier is cut when the message has been transferred. The ID may then be used for another message in the queue ©2010, J.-D. Decotignie SOURCE L_MESSAGE. request L_SENT.indication L_MESSAGE. confirmation Real-Time Networks – WorldFIP 32 DLL ID=n B_DAT prod MSG Réf F_MSG apér BUS ARBITER ID_DAT n RP_DAT_MSG ID_MSG n RP_MSG_NOACK RP_FIN DLL F_MSG reçu DESTINATION(S) L_MESSAGE. indication ©2010, J.-D. Decotignie
Frame Format Timers Real-Time Networks – WorldFIP 33 • PRE = 8 consecutive "1" • FSD = V+ V- V+ 1 V- • FED = V- V+ V- 0 V+ • FCS= CRC 16 (CCITT V41) on CD field Frame Type identifier (ID_xyz) Response request (RP_RQx) Response message (RP_MSG) Response data (RP_DAT_z) Other frames FSS PRE (8 bits) FSD (5 + 1 bits) EB+ Data / address field (CD field) Identifier (2 bytes) Control (8 bits) List of identifier of requested var. transfers (≤ 64 ids) Source + destin. Addr. (2x24 bits) + message (≤256B) Data (up to 128 bytes) empty CD Address and/or data (nx8 bits) EB- FES FED (5 bits) FCS (16 bits) EB- ©2010, J.-D. Decotignie Name Localization Function Value T0 Return time T1 Active BA Absence of RPxx after IDxx T0 T2 Active BA Filling synchronization window EC time T3 Potential BAs Absence of IDxx after RPxx K*N*T0 T4 Consumer no RP_DAT_xx after ID_DAT T0 T5 Active BA no RP_FIN after ID_MSG 2*T0 T6 Source of msg no RP_ACK after RP_MSG_ACK T0 Real-Time Networks – WorldFIP 34 ©2010, J.-D. Decotignie Importance of timer T0 Spatio-temporal aspects Real-Time Networks – WorldFIP 35 • T0 = TR Tmac with 10 ≤ TR ≤ 70 • number of bits in a frame = 61 bits + 8 n User Application Data link Physical 16 bits • transaction duration = 61 Tmac + (61+8n) Tmac + 2 T0 24 bits TR n Efficiency Thoughput (@1Mbit/s) Duration [μs] 10 2 10.1 % 101.3 Kbit/s 158 70 2 5.8% 57.6 Kbit/s 278 10 10 36% 360 Kbit/s 222 70 10 23% 234 Kbit/s 342 21 bits ©2010, J.-D. Decotignie Real-Time Networks – WorldFIP 36 • for periodicity • centralized medium access control • mandatory maximum return time • for validity duration • refreshment status • promptness status • for temporal consistency • based upon refreshment and promptness statuses • for spatial consistency • broadcast of consistency variable ©2010, J.-D. Decotignie
Page 1 and 2: REAL-TIME SYSTEMS II Real-Time Netw
Page 3 and 4: Optical physical layer Topology usi
Page 5 and 6: Bus Arbiter (BA) Signalling a reque
Page 7: Specified explicit request (RQ_Inhi
Page 11 and 12: Spatial consistency Temporal behavi
Page 13 and 14: Example (2) Response time analysis
Page 15: Summary References Real-Time Networ

REAL-TIME SYSTEMS II Real-Time Networking WorldFIP ... - EPFL

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