XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 253

• Manufacturer Part Number: XC912BC32CFU8
• Description: M68HC12B Family Data Sheet
• Manufacturer: Motorola Semiconductor Products

M68HC12B Family — Rev. 8.0
MOTOROLA
TYPE 1 — SINGLE BYTE FROM A SINGLE RESPONDER
TYPE 0 — NO IFR
TYPE 2 — SINGLE BYTE FROM MULTIPLE RESPONDERS
TYPE 3 — MULTIPLE BYTES FROM A SINGLE RESPONDER
HEADER
HEADER
HEADER
HEADER
TSIFR — Transmit Single Byte IFR with No CRC Bit (Type 1 and Type 2)
The BDLC supports the in-frame response (IFR) features of J1850. The four
types of J1850 IFR are shown in
The purpose of the in-frame response modes is to allow multiple nodes to
acknowledge receipt of the data by responding with their personal ID or physical
address in a concatenated manner after they have seen the EOD symbol. If
transmission arbitration is lost by a node while sending its response, it continues
to transmit its ID/address until observing its unique byte in the response stream.
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.
The TSIFR bit is used to request the BDLC to transmit the byte in the BDLC data
register (BDR) as a single byte IFR with no CRC. Typically, the byte transmitted
is a unique identifier or address of the transmitting (responding) node. See
Figure
If the programmer attempts to set the TSIFR bit immediately after the EOD
symbol has been received from the bus, the TSIFR bit remains in the reset state
and no attempt is made to transmit the IFR byte.
1 = If this bit is set prior to a valid EOD being received with no CRC error,
0 = TSIFR bit is cleared automatically, once the BDLC has successfully
Figure 15-14. Types of In-Frame Response
DATA FIELD
DATA FIELD
DATA FIELD
DATA FIELD
once the EOD symbol has been received the BDLC attempts to transmit
the appropriate normalization bit followed by the byte in the BDR.
transmitted the byte in the BDR onto the bus, or TEOD is set, or an error
is detected on the bus.
15-14.
Byte Data Link Communications (BDLC)
CRC
CRC
CRC
CRC
Figure
NB
NB
NB
ID1
ID
15-14.
Byte Data Link Communications (BDLC)
IFR DATA FIELD
IDn
CRC
BDLC Registers
Data Sheet
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