Datasheet

SCEA019 - January 2001
7–78 Texas Instruments GTLP Frequently Asked Questions
Introduction
This information on GTLP and backplane design is presented in the frequently asked-question
(FAQ) format. The GTLP FAQs allow the novice backplane user to learn more about parallel
backplanes and allows the experienced backplane user to better design-in and use the higher
performance of GTLP devices. Any questions not adequately addressed or applications you want
highlighted can be sent to [e-mail] for action and possible future insertion into the FAQs.
1 What is a backplane?
A backplane is a physical and electrical system bus that interconnects several printed circuit
boards though a series of connectors. These buses can vary by the number of layers and
traces and by electrical architecture. Generally, backplanes are passive, particularly in the
telecom market, in which reliability concerns force designers to minimize the number of
backplane components. Backplane transceivers/buffers drive data onto and receive data
directed to PC boards located along the backplane.
2 What is a backplane protocol?
The protocol decides the electrical, logical, and mechanical characteristics of a backplane. In
addition to the standard protocols, many backplane designers prefer to employ proprietary
protocols and architectures. Some of the more popular standard protocols are BLT, MBLT,
2eVME, and 2eSST on VME64x backplanes, PCI, cPCI, PMC, ISA, Multibus, PC/104, and
PC/104+. Of these, VME, PCI and cPCI, collectively, dominate the market. cPCI combines the
robust, rugged VME backplane physical configurations with the electrical performance of the
PCI backplanes.
3 Should I use a parallel or serial architecture?
Part of choosing a protocol is deciding which type of backplane architecture is suited best to
your application. You must choose between parallel and serial architectures, or a combination
of both, and select point-to-point, multidrop, or multipoint data-distribution methods. Parallel
systems require less protocol overhead, which is useful when sending status or control bits
over short distances. Serial implementations offer board saving through the reduction in the
number of board traces (if SERDES devices are used) and supply higher data throughput over
greater distances.