Texas Instruments TMS320TCI648x - Manual (Page 34)

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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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