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Configuration and functionality UM0819
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6 Configuration and functionality
This section describes the functions and configuration of STM802RT1A Ethernet PHY
demonstration board and STM32F107 controller demonstration board.
6.1 Configuration and functionality- ST802RT1 TX mode
Ethernet PHY demonstration board
In this chapter jumper “high” means that the jumper is placed in the position closer to the top
edge of the board and “low” means that the jumper is placed in the position closer to the
bottom edge of the board as shown by
Figure 10 .
Figure 10. Jumper configuration
6.1.1 Boot strap options
The ST802RT1 TX mode PHY uses many of the functional pins as strap options. The values
of these pins are sampled during hardware reset and power up. They are used to strap
signals on the device into specific modes of operation. The ST802RT1 TX mode provides
a simple strap option to automatically configure the device to operate in the modes requiring
no device register configuration. All strap pins have a weak internal pull-ups or pull-downs.
To change the default strap value, the strap pins should be connected directly to V
CC
or
GND with an external 2.2 k
Ω
resistor. The software reset and power-down through the
power-down pin cannot be used to change the strap configuration.
Auto-negotiation
Auto-negotiation is performed as part of the initial set-up of the link. It allows the PHYs
connected to the cable to exchange their key features (speed, PHY type, half or full duplex)
and automatically select the link communication mode. If auto-negotiation is disabled the
chip stays at the speed that is selected by strap pins. If the partner PHY speed is the same,
the link ON state is signaled otherwise no link state is signaled.
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