PEX 8680 Quick Start Hardware Design Guide, Version 1.1
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© 2011 PLX Technology, Inc. All Rights Reserved.
PEX 8680
TDO
TDI
TCK
TMS
TRST#
VCC
from JTAG Controller
from JTAG Controller
from JTAG Controller
to next JTAG device
from previous JTAG device
R
R
R
R = 1K
Figure 15. JTAG Interface Block Diagram
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PCI Express Port Good Indicators
The PEX 8680 provides up to 20 Active-Low “Port Good” Output balls for the PCI Express Port on the
device, PEX_PORT_GOOD[23:16,11:0]#. These Output balls can be used to build the Port Status LED
circuits, to indicate the status of each PEX 8680 Port. Each Port has five states, which are related to Link
Status, Channel Speed, and the Port’s Lane width.
lists the relationship of the LED On/Off
patterns to the Port status.
Table 2. PEX 8680 LED On/Off Patterns, by State
State
LED Pattern
Link is down
Off
Link is up, 5 Gbps, all Lanes are up
On
Link is up, 5 Gbps, reduced Lanes are up
Blinking, 0.5 seconds On, 0.5 seconds Off
Link is up, 2.5 Gbps, all Lanes are up
Blinking, 1.5 seconds On, 0.5 seconds Off
Link is up, 2.5 Gbps, reduced Lanes are up
Blinking, 0.5 seconds On, 1.5 seconds Off
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Debug Functions
(The optional Debug function is primarily intended for prototyping activities. Its use requires assistance
from PLX Technical Support.)
Two major debug functions of the PEX 8680 are External Probe mode (EPM) and SerDes Debug mode
(SDM). The EPM function is for viewing the internal state machines and control signals of the
three station-based modules and the core-based module. The SDM function is for viewing
the 20-bit Receive Bus (elastic buffer exit) and 20-bit Transmit Bus of each Lane of the SerDes,
in the PEX 8680. Two Strapping balls are used to enable either Debug mode function. Pulling down
the STRAP_PROBE_MODE# ball enables the EPM function. Pulling down the
STRAP_SERDES_MODE_EN# ball enables the SDM function. The EPM contains 16 inputs and
39 outputs. The SDM contains 11 inputs and 44 outputs. When either Debug mode is enabled, the
parallel Hot Plug, Port Good, General-Purpose I/O, and Spare balls, as well as two other Strapping balls
are serviced by EPM and SDM inputs or outputs.
Notes: Inputs are marked in
blue
, outputs are marked in
red
.
The maximum frequency of Debug mode Output signals, such as PROCMON (N/C, at location W4), is
125 MHz, with fast rise and fall time. When routing these traces to the mictor connector for scope probing,
50-ohm, single-ended controlled-impedance traces are recommended. To service normal operation and
