LMH0384 Datasheet, PDF (10/16 Pages) National Semiconductor (TI) – 3 Gbps HD/SD SDI Extended Reach and Configurable Adaptive Cable Equalizer

FIGURE 7. Extended 3G Reach Mode State Machine Example
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EXPLANATION OF EXTENDED 3G REACH MODE STATE
MACHINE (Figure 7)
When the LMH0384 is powered on, it will be in normal mode.
If there is no input signal (register 00h, bit 7 = 0) or if the input
cable is longer than a user programmable cable length (i.e.
180m, which means register 03h, bits [7:3] > 10010), then the
device should remain in normal mode.
Once an input signal is detected (register 00h, bit 7 = 1) AND
the detected cable length is shorter than the user pro-
grammed cable length of 180m (register 03h, bits [7:3] <
10010), then the equalizer can enter the extended 3G reach
mode to allow for longer cable lengths at 2.97 Gbps. This re-
quires the following procedure:
1. Force the equalizer to sleep by writing “10” to bits [4:3] of
register 00h.
2. Turn on the extended 3G reach mode by writing “1” to
bit 2 of register 00h.
3. Wait at least 1ms.
4. Set the sleep mode to auto by writing “01” to bits [4:3] of
register 00h. Alternately, sleep mode may be set to off by
writing “00” to bits [4:3] of register 00h.
The equalizer remains in extended 3G reach mode until the
cable length is changed. If the cable length is changed, the
input signal drops out momentarily. Once this happens (reg-
ister 00h, bit 7 = 0), then the following procedure must be used
to set the device back to normal mode:
1. Force the equalizer to sleep by writing “10” to bits [4:3] of
register 00h.
2. Turn off the extended 3G reach mode by writing “0” to
bit 2 of register 00h.
3. Wait at least 1ms.
4. Set the sleep mode to auto by writing “01” to bits [4:3] of
register 00h. Alternately, sleep mode may be set to off by
writing “00” to bits [4:3] of register 00h.
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