MC68HC908AS60ACFN FREESCALE [Freescale Semiconductor, Inc], MC68HC908AS60ACFN Datasheet - Page 358

• Manufacturer Part Number: MC68HC908AS60ACFN
• Description: M68HC08 Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Byte Data Link Controller (BDLC)
TSIFR, TMIFR1, and TMIFR0 — Transmit In-Frame Response Control Bits
358
These three bits control the type of in-frame response being sent. The programmer should not set
more than one of these control bits to a 1 at any given time. However, if more than one of these three
control bits are set to 1, the priority encoding logic will force these register bits to a known value as
shown in
they will be encoded as 010. However, when these bits are read back, they will read 011.
The BDLC supports the in-frame response (IFR) feature of J1850 by setting these bits correctly. The
four types of J1850 IFR are shown below. 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, because the first bit of the IFR is always
passive, a normalization bit (active) 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 up their response.
NB = Normalization Bit
ID = Identifier (usually the physical address of the responder(s))
HEADER = Specifies one of three frame lengths
HEADER
HEADER
HEADER
HEADER
Table
TYPE 0 — NO IFR
TYPE 1 — SINGLE BYTE TRANSMITTED FROM A SINGLE RESPONDER
TYPE 2 — SINGLE BYTE TRANSMITTED FROM MULTIPLE RESPONDERS
TYPE 3 — MULTIPLE BYTES TRANSMITTED FROM A SINGLE RESPONDER
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
Write/Read
27-4. For example, if 011 is written to TSIFR, TMIFR1, and TMIFR0, then internally
TSIFR
0
1
0
0
Figure 27-18. Types of In-Frame Response (IFR)
DATA FIELD
DATA FIELD
Table 27-4. BDLC Transmit In-Frame Response
DATA FIELD
DATA FIELD
Write/Read
TMIFR1
X
0
1
0
Control Bit Priority Encoding
CRC
CRC
CRC
CRC
Write/Read
TMIFR0
0
X
X
1
NB
NB
NB
ID1
ID
Actual
TSIFR
IFR DATA FIELD
0
1
0
0
TMIFR1
Actual
0
0
1
0
ID N
TMIFR0
Actual
Freescale Semiconductor
0
0
0
1
(OPTIONAL)
CRC