DS90CR212

DS90CR211/DS90CR212 21-Bit Channel Link July 1997 DS90CR211/DS90CR212 21-Bit Channel Link General Description The DS90CR211 transmitter converts 21 bits of CMOS/TTL data into three LVDS (Low Voltage Differential Signaling) data streams. A phase-locked transmit clock is transmitted in parallel with the data streams over a fourth LVDS link. Every cycle of the transmit clock 21 bits of input data are sampled and transmitted. The DS90CR212 receiver converts the LVDS data streams back into 21 bits of CMOS/TTL data. At a transmit clock frequency of 40 MHz, 21 bits of TTL data are transmitted at a rate of 280 Mbps per LVDS data channel. Using a 40 MHz clock, the data throughput is 840 Mbit/s(105 Mbyte/s). The multiplexing of the data lines provides a substantial cable reduction. Long distance parallel single-ended buses typically require a ground wire per active signal (and have very limited noise rejection capability). Thus, for a 21-bit wide data bus and one clock, up to 44 conductors are required. With the Channel Link chipset as few as 9 conductors (3 data pairs, 1 clock pair and a minimum of one ground) are needed. This provides a 80% reduction in required cable width, providing a system cost savings, reduces connector physical size, and reduces shielding requirements due to the cables smaller form factor. The 21 CMOS/TTL inputs can support a variety of signal combinations. For example, 5 4-bit nibbles plus 1 control, or 2 9-bit (byte + parity) and 3 control. Features n n n ...