PEX 8680 Quick Start Hardware Design Guide, Version 1.1
18
© 2011 PLX Technology, Inc. All Rights Reserved.
Ball/Signal Name
Functions
Default
These pins MUST be strapped to
01b(LH). STRAP_RESERVED0
can remain unconnected(N/C)
STRAP_RESERVED[3:2]
Factory Test Only. NOTE:
These pins MUST be strapped to
00b(LL). They can also remain
unconnected(N/C)
Internal pull-downs
STRAP_RESERVED16
Factory Test Only. Must be tied
directly to Ground.
No internal pull-up or pull-
down.
STRAP_RESERVED17#
Factory Test Only.
Internal pull-up
STRAP_NT_ENABLE#
Enable NT function
Internal pull-up
STRAP_NT_UPSTRM_PORTSEL[4:0]
NT Port select
Internal pull-downs
STRAP_STN0_PORTCFG[1:0]
Port configuration per station.
LL = x4x4x4x4
LH = x16
HL = x8x8
HH = x8x4x4
Internal pull-downs
STRAP_STN1_PORTCFG[1:0]
STRAP_STN2_PORTCFG[1:0]
STRAP_STN3_PORTCFG[1:0]
STRAP_STN4_PORTCFG[1:0]
STRAP_STN5_PORTCFG[1:0]
STRAP_DEBUG_SEL[1:0]
Factory Test Only.
Internal pull-downs
STRAP_TESTMODE[4:0]
Test mode function select.
Defines
PEX_PORT_GOOD[23:0]# and
GPIO[42:24] signal functionality.
NOTE: 00h is not a valid setting.
For normal operation, these balls
should be pulled to 0Dh by
external pull-ups.
Internal pull-downs
STRAP_UPSTRM_PORTSEL[4:0]
Upstream Port select
Internal pull-downs
STRAP_VS_MODE[2:0]
Determines the number of Virtual
Switches that are enabled. If
000b, no Virtual Switches are
enabled and the device is in
Mode-1 and operates as a single
switch.
Internal pull-downs
10
GPIO Balls
The PEX 8680 has 43 GPIO balls – 23 are dedicated GPIO balls, and 20 share GPIO and
PEX_PORT_GOOD[23:16,11:0]# functions in standard operation. Depending on the settings of the Test
mode balls, STRAP_TESTMODE[4:0], the GPIO balls can be set as input or output. If Serial Hot Plug is
implemented, using external I2C I/O Expanders, it is recommended that the 19 dedicated GPIO balls be
configured as PERST# outputs (STRAP_TESTMODE setting 0Ch or 0Dh) and routed directly to the slots,
bypassing the I/O Expander.
11
Power Supplies, Sequencing, and De-Coupling
The switch’s maximum power consumption is approximately 18W. Special cooling requirements may exist,
depending upon the system environment. (Refer to the
PEX 8680 Data Book
for details).
