Datasheet

Byte Data Link Controller Module
Functional Description
MC9S12DP256 — Revision 1.1
Byte Data Link Controller Module
Valid EOD Symbol If the passive to active transition beginning the next data bit or symbol
occurs between T
rvp3(Min)
and T
rvp3(Max)
, the current symbol would be
considered a valid EOD symbol.See Figure 119(4).
Figure 120 J1850 VPW EOF and IFS Symbols
Valid EOF & IFS
Symbol
In Figure 120(1), if the passive to active transition beginning the SOF
symbol of the next message occurs between T
rv4(Min)
and T
rv4(Max)
, the
current symbol will be considered a valid EOF symbol.
If the passive to active transition beginning the SOF symbol of the next
message occurs after T
rv5(Min)
, the current symbol will be considered a
valid EOF symbol followed by a valid IFS symbol. See Figure 120(2). All
nodes must wait until a valid IFS symbol 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
tv5(Min)
, the bus is considered to be
idle, and any node wishing to transmit a message may do so
immediately.
(2) Valid EOF + IFS Symbol
280µs
300µs
T
rv4(Min)
T
rv4(Max)
(1) Valid EOF Symbol
Active
Passive
Active
Passive
T
rv5(Min)
Freescale Semiconductor, I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
nc...