Instruction Manual

Chapter 3 Hardware
ETX-PVR Reference Manual 37
Power Control Signals
The ETX-PVR supports various power control signals provided through the baseboard to control the
ETX-PVR and the power supply.
• The Power Good input signal (PWGIN) is provided from an external input typically from the external
power supply (ATX) to the baseboard. This signal is typically an active-high input to the ETX
baseboard and indicates to the ETX module it can begin the boot process. This Power Good signal can
also be used as an active-low reset input to the ETX module.
• The Power Suspend signal (5V_SB) must be provided through the power supply interface for standby
operation, typically an ATX power supply. The power supply must provide a 5 volt
130mA stand-by power source for this function to be available.
• The Power On signal (PS_ON) is provided by the ETX module to the PS_ON input of an ATX power
supply allowing it to switch to main output power from a standby state. This signal is used in
conjunction with the 5V_SB supplied to the ETX module from the ATX power supply.
• The Power Button Input signal (PWRBTN*) provides a ground temporally through a momentary-
contact switch or through an open collector driver to the ATX power supply. This signal is used in
conjunction with the PS_ON and the 5V_SB signals from the ATX power supply to activate the power
control function of the power supply.
• A voltage monitor on the ETX-PVR tracks the VCC voltage (+5 volts) state by monitoring the +3.3V
generated on the ETX module. When the +3.3V drops below 3.0V or the Reset Button signal goes low,
the voltage monitor sends a reset pulse to the CPU and the I/O Hub.
* indicates Active Low.
Power Management Signals
The ETX-PVR supports various power management signals described in the following list.
• The External System Management Interrupt (EXTSMI) signal is routed to the baseboard through J4 to
allow external circuitry to initiate an SMI for the ETX module.
• The Resume Reset input (RSMRST*) signal to the ETX module may be driven low by external control
circuitry to reset the power management logic on the ETX module.
• The System Management Bus Alert input (SMBALRT*) signal is used by SMBus devices to indicate an
event on the SMBus to the ETX module.
• The Battery Low input (BATLOW*) signal is used by external voltage monitoring circuitry to indicate
the system battery is low to the ETX module.
* indicates Active Low.
Speaker
The signal lines for a speaker port with 0.1-watt drive are provided through the J4 connector to the
baseboard where the speaker must be located.
The I/O Hub provides the speaker output signal, but the output drive circuit must be implemented on the
baseboard.
Real Time Clock (RTC)
The ETX-PVR supports a Real Time Clock (RTC) and CMOS RAM for the BIOS Setup Utility. The RTC
and 256 byte of CMOS RAM are included inside the I/O Hub. The RTC and CMOS are backed up through
the BAT pin on J4 with a battery located on the baseboard. If the battery is not present, the BIOS has a
battery-free boot option to complete the boot process.