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SRIO Functional Description
Table 11. SERDES Transmit Channel Configuration Register n (SERDES_CFGTXn_CNTL) Field
Descriptions (continued)
Bit
Field
Value
Description
15–12
DE
0000b–1111b
De-emphasis. Selects one of 15 output de-emphasis settings from 4.76 to 71.42%.
De-emphasis provides a means to compensate for high frequency attenuation in the
attached media. It causes the output amplitude to be smaller for bits which are not
preceded by a transition than for bits which are. See
Table 12
.
11–9
SWING
000b–111b
Output swing. Selects one of 8 outputs amplitude settings between 125 and
1250mV
dfpp
. See
Table 13
.
8
CM
Common mode. Adjusts the common mode to suit the termination at the attached
receiver. For output swing settings above 750mV, this reduced common mode can
cause distortion of the waveform. Under these conditions, this bit should be set high to
offset some of the common mode reduction.
0
Normal common mode. Common mode not adjusted.
1
Raised common mode. Common mode raised by 5% of difference between RIOTXn
and RIOTXn
7
INVPAIR
Invert polarity. Inverts the polarity of RIOTXn and RIOTXn.
0
Normal polarity. RIOTXn is considered to be positive data and RIOTXn negative.
1
Inverted polarity. RIOTXn is considered to be negative data and RIOTXn positive.
6–5
RATE
Operating rate. Selects full, half, or quarter rate operation.
00b
Full rate. Two data samples taken per PLL output clock cycle.
01b
Half rate. One data sample taken per PLL output clock cycle.
10b
Quarter rate. One data sample taken every two PLL output clock cycles.
11b
Reserved
4–2
BUSWIDTH
000b
Bus width. Always write 000b to this field, to indicate a 10-bit-wide parallel bus to the
clock. All other values are reserved. See
Section 2.3.2.1
for an explanation of the bus.
1
Reserved
0
Always write 0 to this reserved bit.
0
ENTX
Enable transmitter
0
Disable this transmitter.
1
Enable this transmitter.
Table 12. DE Bits of SERDES_CFGTXn_CNTL
Amplitude Reduction
DE Bits
%
dB
0000b
0
0
0001b
4.76
–0.42
0010b
9.52
–0.87
0011b
14.28
–1.34
0100b
19.04
–1.83
0101b
23.8
–2.36
0110b
28.56
–2.92
0111b
33.32
–3.52
1000b
38.08
–4.16
1001b
42.85
–4.86
1010b
47.61
–5.61
1011b
52.38
–6.44
1100b
57.14
–7.35
1101b
61.9
–8.38
1110b
66.66
–9.54
1111b
71.42
–10.87
Serial RapidIO (SRIO)
34
SPRUE13A – September 2006
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