Datasheet

SCEA022
7–272
Achieving Maximum Speed on Parallel Buses With Gunning Transceiver Logic (GTLP)
4 Measurements Using Texas Instruments GTLP Evaluation Module
Theoretical considerations concerning the two transmission modes discussed in the previous
sections can be confirmed by measurements, using the GTLP demonstration backplane.
The evaluation module (EVM) (see Figure 15) is a good model for a typical parallel-backplane
system as found, for example, in telecom applications.
Figure 15. GTLP Demonstration Backplane
Altogether, 48 bits run in parallel over the 19-inch backplane, which has 20 slots, each 1 inch
apart. The connectors are fully integrated onto the backplane, while the number of modules can
vary. GTLPH1655 devices are used as the interface.
Different bus characteristics can be realized and shown using this EVM.
By using the EVM, it is possible to show the effect of termination resistances on signal quality, as
well as different load conditions, due to a different number of modules on the bus. Also, the
clock frequency is variable.
Figure 16 shows the layout of the driver card. Using a jumper, the transmitter can be switched
from the system-synchronous clock mode to the source-synchronous clock mode.