128
Peripheral Local Bus
Figure 65.
Peripheral Bus Latched Bidirectional Single Load Topology
Table 74.
Routing Guideline Latched Bidirectional Latch Single Load
Parameter
Routing Guidelines
Reference Plane
Route over unbroken ground plane or power plane. If
routing over power plane maintain this consistency
throughout the topology.
Breakout
5 mils on 5 mils spacing. Maximum length of breakout
region is 500mils.
Routing
Microstrip or stripline or combination of microstip and
stripline.
Motherboard Impedance (for both microstrip and
stripline)
50 ohms +/- 15%
Add-in card Impedance (for both microstrip and
stripline)
60 ohms +/- 15%
Trace Spacing (center to center)
•
> 12 mils between all AD lines
•
> 20 mils must be maintained from all other
signals or vias.
Trace Length TL1
2.0” to 10.0”
Trace Length to TL2
0.5” to 2.0”
Trace Length to strapping resistors
0.5” to 3.0” from the last device on the bus.
Routing Recommendations
Number of vias for microstrip < 2
Number of vias for stripline < 4
Route as daisy-chain only.
Address latches for 16 bit implementations may be in
any of the device locations for ease of routing.
T L1
TL2
Latch
F las h
Summary of Contents for 80331
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