Datasheet

Byte Data Link Controller Module
Register Descriptions
MC9S12DP256 — Revision 1.1
Byte Data Link Controller Module
The BDLC supports the In-frame Response (IFR) feature of J1850 by
setting these bits correctly. The four types of J1850 IFR are shown in
Types of In-Frame Response. The purpose of the in-frame response
modes is to allow single or multiple nodes to acknowledge receipt of
the data by responding to a received message after they have seen
the EOD symbol. For VPW modulation, the first bit of the IFR is
always passive; therefore, an active normalization bit must be
generated by the responder and sent prior to its ID/address byte.
When there are multiple responders on the J1850 bus, only one
normalization bit is sent which assists all other transmitting nodes to
sync their responses.
Figure 127 Types of In-Frame Response
TSIFR
— Transmit Single Byte IFR with no CRC (Type 1 or 2)
This bit is used to request the BDLC to transmit the byte in the BDLC
Data Register (DLCBDR) as a single byte IFR with no CRC. Typically,
the byte transmitted is a unique identifier or address of the
transmitting (responding) node.
1 = If this bit is set prior to a valid EOD being received with no CRC
error, once the EOD symbol has been received the BDLC will
attempt to transmit the appropriate normalization bit followed
by the byte in the DLCBDR.
SOF
Header Data Field CRC
EOD
Type 0 – No IFR
Header
Data Field CRC
EOD
Type 3 – Multiple Bytes From a Single Responder (with or without CRC)
Header Data Field CRC
EOD
Type 1 – Single Byte From a Single Responder (without CRC)
Header Data Field
CRC
EOD
Type 2 – Single Byte From Multiple Responders (without CRC)
ID1
ID n
IFR Data Field CRC
NB
NB
NB
ID
SOF
SOF SOF
EOF
EOD EOF
EOD EOF
EOD EOF
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