M68HC12A4EVB Freescale Semiconductor, M68HC12A4EVB Datasheet - Page 240

• Manufacturer Part Number: M68HC12A4EVB
• Manufacturer: Freescale Semiconductor

Specifications of M68HC12A4EVB

• Lead Free Status / Rohs Status: Not Compliant

Byte Data Link Communications (BDLC)
15.9.5 BDLC Analog Roundtrip Delay Register
Read: Anytime
Write: Once in normal modes or anytime in special mode
BARD programs the BDLC to compensate for various delays of external transceivers.
ATE — Analog Transceiver Enable Bit
RXPOL — Receive Pin Polarity Bit
BO3–BO0 — BARD Offset Bits
240
The ATE bit is used to select either the on-board or an off-chip analog transceiver.
This bit selects the polarity of an incoming signal on the receive pin. Some external analog transceivers
invert the receive signal from the J1850 bus before feeding it back to the digital receive pin.
These bits are used to compensate for the analog transceiver roundtrip delay.
expected transceiver delay with respect to BARD offset values.
0 = Select off-chip analog transceiver.
1 = Select on-board analog transceiver.
0 = Select inverted polarity, where external transceiver inverts the receive signal.
1 = Select normal/true polarity; true non-inverted signal from J1850 bus, for example, the external
transceiver does not invert the receive signal.
Address:
This device does not contain an on-board transceiver; ATE should be
cleared for proper operation.
Reset:
Read:
Write:
Figure 15-17. BDLC Analog Roundtrip Delay Register (BARD)
$00FC
Bit 7
ATE
1
= Unimplemented
RXPOL
M68HC12B Family Data Sheet, Rev. 9.1
6
1
5
0
0
NOTE
4
0
0
BO3
3
0
BO2
2
1
BO1
1
1
Table 15-5
Freescale Semiconductor
Bit 0
BO0
1
shows the