XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 252

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

Byte Data Link Communications (BDLC)
Data Sheet
252
NBFS — Normalization Bit Format Select Bit
TEOD — Transmit End of Data Bit
TSIFR, TMIFR1, TMIFR0 — Transmit In-Frame Response Bits
This bit controls the format of the normalization bit (NB). (See
SAE J1850 encourages using an active long (logic 0) for in-frame responses
containing cyclical redundancy check (CRC) and an active short (logic 1) for
in-frame responses without CRC.
This bit is set by the programmer to indicate the end of a message is being sent
by the BDLC. It appends an 8-bit CRC after completing transmission of the
current byte. This bit also is used to end an in-frame response (IFR). If the
transmit shadow register is full when TEOD is set, the CRC byte is transmitted
after the current byte in the Tx shift register and the byte in the Tx shadow
register have been transmitted. (See
a description of the transmit shadow register.) Once TEOD is set, the transmit
data register empty flag (TDRE) in the BDLC state vector register (BSVR) is
cleared to allow lower priority interrupts to occur. (See
Vector
These bits control the type of in-frame response being sent. Only one of these
bits should be set at a time. If more than one are set, the priority encoding logic
forces the bits to a known value as shown in
written to TSIFR, TMIFR1, and TMIFR0, then internally they are encoded as
010. However, when these bits are read back, they read 011.
1. Shaded cells indicate bits which do not affect internal interpretation. These bits read
0 = NB that is received or transmitted is a 1 when the response part of an
1 = NB that is received or transmitted is a 0 when the response part of an
1 = Transmit end-of-data (EOD) symbol
0 = TEOD bit is cleared automatically at the rising edge of the first CRC bit
TSIFR
back as written.
0
1
0
0
in-frame response (IFR) ends with a CRC byte. NB that is received or
transmitted is a 0 when the response part of an in-frame response (IFR)
does not end with a CRC byte.
in-frame response (IFR) ends with a CRC byte. NB that is received or
transmitted is a 1 when the response part of an in-frame response (IFR)
does not end with a CRC byte.
that is sent or if an error is detected. When TEOD is used to end an IFR
transmission, TEOD is cleared when the BDLC receives back a valid
EOD symbol or an error condition occurs.
Register.)
Table 15-3. Transmit In-Frame Response Bit Encoding
Byte Data Link Communications (BDLC)
Write/Read
TMIFR1
0
1
0
(1)
TMIFR0
0
1
15.8.3 Rx and Tx Shadow Registers
TSIFR
0
1
0
0
Table
Internal Interpretation
15-3. For example, if 011 is
TMIFR1
M68HC12B Family — Rev. 8.0
15.9.3 BDLC State
0
0
1
0
Figure
TMIFR0
0
0
0
1
MOTOROLA
15-14.)
for