PEX 8509RDK Hardware Reference Manual v1.1
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© 2007, PLX Technology, Inc. All rights reserved.
The PERST# signal supplied to J4 is directly controlled by the HPC (HP_PERST[3]#). By default, the Hot
Plug control over slot J4 in not enabled. The user can enable Hot Plug control of power and reset to J4,
by placing switch SW4, pin 1 to the OFF position.
2.7 Serial
EEPROM
The PEX 8509RDK contains an 8-pin DIP socket for a serial EEPROM (U2). The board is populated with
a blank Atmel AT25080A 8-Kbit device. To use the serial EEPROM, place a shunt between pins 1 and 2
of JP2 (see section 3.4 for more details). The AT25080A device can directly interface to the PEX8509.
2.8 I2C
Interface
The PEX 8509 implements an I2C slave interface, which allows an external I2C master to read and write
device registers through an out-of-band mechanism. The PEX 8509 I2C interface is accessible via a 7-bit
address, at data rates up to 400kbits/sec. The RDK provides two cascaded 2x2, 0.1” pitch headers (JP3
and JP4), which interface to the PEX 8509’s I2C port. This allows for cascading multiple RDKs together
using standard ribbon cable, or connecting various 3
rd
party I2C test equipment such as the Total Phase
Aardvark I2C controller.
Figure 2-3. I2C Connector Orientation for Aardvard I2C Controller
2.9 Power
Distribution
2.9.1 Power
Generation/Conversion
The PEX 8509RDK has two sources for DC power. The first source is the card edge connector (P1). The
x4 connector provides up to 2.1A at +12V and 3.0A at +3.3V. Card edge power is intended to power only
RDK board components and slot J4. Slots J1, J2 and J3 receive power via a 4-pin ATX hard disk
connector (J5). Add-in cards that require more that 25W of power (such as graphics cards) should use
slots J1, J2 and/or J3. These slots are power limited only by the ATX power supply that is used.
PEX8509 core and 1.0V supply is derived from the +3.3V rail through a Micrel MIC49150 LDO
regulator (U13). The PEX 8509’s +3.3V I/O supply receives power directly from the +3.3V card edge
power rail. The VTT supply for the PEX8509 PCI Express transmitters, is regulated from the +3.3V card
edge power via a Maxim MAX1806 adjustable LDO regulator (U14). The regulator output voltage is
normally set to +1.50V, but can be adjusted by changing the values of R98 and R102.
The ATX 4-pin connector pr12V and +5V DC power. The +5V is converted down to +3.3V for
slots J1, J2 and J3 through a Bel S7AH-08B330/-08E1A0 non-isolated DC/DC converter (U12). The +12V
power rail is used directly.
1
2
1
2
3
3
4
4
JP3
JP4
