J1850 Vpw Eof And Ifs Symbols - Freescale Semiconductor MPC5200B User Manual

Active
Passive
Active
Passive
• Valid EOF & IFS Symbol
In Figure 20-7(1), if the passive to active transition beginning the SOF symbol of the next message occurs between T
T , the current symbol will be considered a valid EOF symbol.
rv4(Max)
If the passive to active transition beginning the SOF symbol of the next message occurs after T
considered a valid EOF symbol followed by a valid IFS symbol. See
time has expired before beginning transmission. However, due to variations in clock frequencies and bus loading, some nodes may
recognize a valid IFS symbol before others, and immediately begin transmitting. Therefore, anytime a node waiting to transmit
detects a passive to active transition once a valid EOF has been detected, it should immediately begin transmission, initiating the
arbitration process.
• Idle Bus
If the passive to active transition beginning the SOF symbol of the next message does not occur before T
considered to be idle, and any node wishing to transmit a message may do so immediately.
Freescale Semiconductor
300µs
280µs
T
rv4(Min)
Figure 20-7. J1850 VPW EOF and IFS Symbols
MPC5200B Users Guide, Rev. 1
(1) Valid EOF
T
rv4(Max)
(2) Valid EOF+
T
rv5(Min)
rv5(Min)
Figure 20-7(2). All nodes must wait until a valid IFS symbol
Functional Description
Symbol
IFS Symbol
and
rv4(Min)
, the current symbol will be
, the bus is
tv5(Min)
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