Driver Cards
2-25
GTLP EVM Board Typical Test and Setup Configuration
2.11.3 Source-Synchronous Clock/System-Clock Selection
Backplanes usually have a system-wide synchronous clock. A system clock
provides an absolute reference time signal from the clock card to every
daughter card at exactly the same time. Source-synchronous clock operation
is different because it allows the absolute system clock to be sent by the
backplane driver along with the data. In the EVM, this is implemented with the
SN74GTLP1394 transceiver on all daughter cards. This transceiver acts as
the driver on the driver cards and as the receiver on the receiver cards. The
SN74GTLP1394 has ERC that is set to the fast edge rate in conjunction with
the JB3 selection.
Source-synchronous clock operation provides a relative clock to all receiver
cards, which removes the flight-time delay restrictions required when an
absolute system clock is used. The flight-time delay depends primarily on bus
length and bus loading.
The driver card uses JB2 to select the transfer mode of operation and to drive
the MODESEL line. Source-synchronous clock operation is selected when the
JB2 jumper shorts the pins, and system-clock operation is selected when the
pins are open (see Figure 2–21). When JB2 is shorted, the SN74GTLP1394
drives the GTLP clock line with a phased system clock. When JB2 is open,
there is no activity on the GTLP clock line. The following options are available:
-
JB2 shorted
Source-synchronous clock transfer
-
JB2 open
System-clock transfer
Figure 2–21. JB2 Set to Source-Synchronous Clock (Left) or System-Clock (Right)
Operation
Summary of Contents for GTLP
Page 1: ...June 2001 Standard Linear Logic GTLP Evaluation Module EVM User s Guide ...
Page 2: ...Printed in U S A 0601 SCEA023 ...
Page 3: ...GTLP Evaluation Module EVM User s Guide SCEA023 June 2001 Printed on Recycled Paper ...
Page 12: ...Tables x ...
Page 26: ...Connectors 2 10 Figure 2 7 AMP Single Line Model Data Sheet ...
Page 65: ...Monitored Waveforms 4 8 ...
Page 71: ...Damage to the Daughter Cards 5 6 ...
Page 79: ...Board Layouts and Schematics A 8 Figure A 4 Backplane Schematic ...
Page 81: ...Board Layouts and Schematics A 10 Figure A 6 Driver Card Schematic ...