For optimal design, the DS40MB200 must be configured to route incoming data correctly as well as to provide the best signal quality. The following design procedures must be observed:

1. The DS40MB200 must be configured to provide the correct multiplexer and buffer routes in order to satisfy system requirements. In order to set the appropriate multiplexer control settings, refer to Table 7-1. To configure the buffer control settings, refer to Table 7-2. For example, consider the case where the designer wishes to route the input from Switch Card A (SIA0_0±) to the output for the line card (LO_0±). To accomplish this, set MUX_S0 = 1 (select SIA0_0±). For the other direction from line card output to switch card, set LB0A = 1 and LB0B = 1 so that the input from the line-card is buffered to both Switch Card A (SOA_0±) and Switch Card B (SOB_0±).
2. The DS40MB200 is designed to be placed at an offset location with respect to the overall channel attenuation. To optimize performance, the multiplexer buffer transmit pre-emphasis can be tuned to extend the trace length reach while also recovering a solid eye opening. To tune transmit pre-emphasis on either the line card side or switch card side, refer to Table 7-3 and Table 7-4 for recommended pre-emphasis control settings according to the length of FR4 board trace connected at the DS40MB200 output. For example, if 40 inches of FR4 trace is connected to the switch card output, set PreS_[1:0] = (1, 1) for VOD = 1200 mVpp and –9 dB of transmit pre-emphasis.