Freescale Semiconductor MPC5200B User Manual page 692

msb 0
R 0
W
RESET: 0
READ: any time
WRITE: write once in normal and emulation modes.
Register functionality modified in special test mode.
Writes to unimplemented bits 7, 5 are ignored.
—
RXPOL Receive Pin Polarity (Bit 6)
The Receive pin Polarity bit is used to select the polarity of incoming signal on the receive pin. Some external analog transceiver inverts the
receive signal from the J1850 bus before feeding back to the digital receive pin.
1 = Select normal/true polarity; true non-inverted signal from J1850 bus, i.e., the external transceiver does not invert the receive
signal.
0 = Select inverted polarity, where external transceiver inverts the receive signal.
—
BO4-BO0 BDLC Analog Roundtrip Delay Offset Field (Bits 4-0)
BO[4:0] adjust the transmitted symbol timings to account for the differing roundtrip delays found in different SAE J1850 analog transceivers.
The allowable delay range is from 0 µs to 31 µs, with a nominal target of 16 µs (reset value). Refer to
corresponding to the expected transceiver delays and the resultant transmitter timing adjustment (in mux interface clock periods (t
to the analog transceiver device specification for the expected roundtrip delay through both the transmitter and the receiver. The sum of these
two delays makes up the total roundtrip delay value.
For Digital Loopback test, the Analog Roundtrip Delay Offset Field should be set to 0µs.
Table 20-7. BARD Values vs. Transceiver Delay and Transmitter Timing Adjustment
BARD Offset Bits BO[4:0]
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
01100
01101
01110
Freescale Semiconductor
Table 20-6. BDLC Analog Round Trip Delay Register
1 2
RXPOL 0
1 0
= Unimplemented
Corresponding Expected
Transceiver's delays (
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MPC5200B Users Guide, Rev. 1
3 4 5
BO4 BO3 BO2
1 0 0
NOTE
Transmitter Symbol Timing
µ
s) Adjustment (
Memory Map and Registers
6 7 lsb
BO1 BO0
0 0
Table 20-7 for the BO[4:0] values
)). Refer
bdlc
t
1
)
bdlc
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
20-13