Bdlc analog round trip delay register -13 – Freescale Semiconductor MPC5200B User Manual
Page 692
Memory Map and Registers
MPC5200B Users Guide, Rev. 1
Freescale Semiconductor
20-13
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
for the BO[4:0] values
corresponding to the expected transceiver delays and the resultant transmitter timing adjustment (in mux interface clock periods (t
bdlc
)). Refer
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.
NOTE
For Digital Loopback test, the Analog Roundtrip Delay Offset Field should be set to 0
µs.
Table 20-6. BDLC Analog Round Trip Delay Register
msb 0
1
2
3
4
5
6
7 lsb
R
0
RXPOL
0
BO4
BO3
BO2
BO1
BO0
W
RESET:
0
1
0
1
0
0
0
0
= Unimplemented
Table 20-7. BARD Values vs. Transceiver Delay and Transmitter Timing Adjustment
BARD Offset Bits BO[4:0]
Corresponding Expected
Transceiver’s delays (
µ
s)
Transmitter Symbol Timing
Adjustment (
t
bdlc
)
1
00000
0
0
00001
1
1
00010
2
2
00011
3
3
00100
4
4
00101
5
5
00110
6
6
00111
7
7
01000
8
8
01001
9
9
01010
10
10
01011
11
11
01100
12
12
01101
13
13
01110
14
14