Texas Instruments | DP83848 - Single 10/100 Mb/s Ethernet Transceiver Ini During Pwr Dwn Mode (Rev. A) | Application notes | Texas Instruments DP83848 - Single 10/100 Mb/s Ethernet Transceiver Ini During Pwr Dwn Mode (Rev. A) Application notes

Texas Instruments DP83848 - Single 10/100 Mb/s Ethernet Transceiver Ini During Pwr Dwn Mode (Rev. A) Application notes
Application Report
SNOA463A – September 2005 – Revised April 2013
AN-1402 DP83848 - Single 10/100 Mb/s Ethernet
Transceiver Initialization During Power Down Mode
.....................................................................................................................................................
ABSTRACT
This application report details the procedure to put the device into Power Down mode during initialization,
configure the registers of the device to the desired mode, and then exit Power Down.
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Contents
Introduction ..................................................................................................................
Power Down Mode Functionality ..........................................................................................
2.1
Note on Dual Function PWR_DOWN/INT Pin .................................................................
Power Down Configuration Sequence ...................................................................................
3.1
Initialization into Power Down Mode ............................................................................
3.2
Configuration During Power Down Mode .......................................................................
3.3
Exit from Power Down Mode .....................................................................................
Summary .....................................................................................................................
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2
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4
List of Figures
1
Initialization Via Pull Down Resistor ...................................................................................... 3
2
Intitialization Via Tri-state Driver .......................................................................................... 3
3
Initialization Via Driver ...................................................................................................... 3
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SNOA463A – September 2005 – Revised April 2013
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AN-1402 DP83848 - Single 10/100 Mb/s Ethernet Transceiver Initialization
During Power Down Mode
Copyright © 2005–2013, Texas Instruments Incorporated
1
Introduction
1
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Introduction
Certain systems or applications require the Ethernet network connection be held in a disconnected state
or a Power Down mode until the rest of the system is powered up, initialized and ready to accept network
traffic. This requirement is in addition to the ability to power down from a normal powered up operating
mode.
Texas Instruments DP83848 10/100 Mb/s single port Physical Layer device is designed with an option to
support initialization during a Power Down mode at system power up. This option can be implemented
using external logic, an external resistor, or a combination of logic and a resistor.
2
Power Down Mode Functionality
During Power Down mode, the DP83848 core functions are disabled. This includes the line driver, the
receiver and the MII/RMII interface. Management entities can still access the internal registers through the
MDIO when the device is in this Power Down mode. Upon entering and exiting Power Down mode, the
registers will preserve their configuration.
2.1
Note on Dual Function PWR_DOWN/INT Pin
The PWR DOWN/INT pin is a dual function pin. By default, the pin acts as an active low power down
input. When configured via register access, the pin can alternately operate as an active low interrupt
output. In this case, interrupts are asynchronously indicated by asserting the interrupt pin.
To configure interrupts, the user must set the INTEN bit (MICR bit 0) to configure the PWRDN_INTN pin
as an active low interrupt pin. When interrupts are enabled, the PWRDN_INTN pin no longer acts as a
power down input.
3
Power Down Configuration Sequence
The PWR_DOWN/INT pin (Pin 7) of the DP83848 is designed with an internal weak pull up. By default,
this pin functions as a power down input.
During normal operation or upon initial power up, the DP83848 can be put in Power Down mode by
asserting the PWR_DOWN/INT pin (Pin 7) low. This is equivalent to setting bit 11 (Power Down mode) in
the Basic Mode Control Register, BMCR (0x00h). In this mode, the PHY is disabled, but still supports
reads and writes to the registers.
Note that the status reflected in the BMCR power down bit is an OR function of the value written via MDIO
access and the value asserted via the PWR_DOWN/INT pin. If the PWR_DOWN/INT pin is asserted low,
attempts to clear the BMCR power down bit through MDIO accesses will be unsuccessful.
3.1
Initialization into Power Down Mode
The PWR_DOWN/INT pin can be asserted to a low state by one of two methods:
• Using an external pull-down resistor (See Figure 1).
• Directly driving the PWRDOWN/INT pin to a logic low level (See Figure 2 or Figure 3).
Note that using an external resistor (Figure 1) or using a logic driver (Figure 3) prevents the
PWR_DOWN/INT pin from normal interrupt operation. When configured as an interrupt with one of these
connections, the pin would be pulled down or driven low, effectively signaling an interrupt.
Using a tri-state driver and a pull up resistor (Figure 2), interrupt capability can be maintained. However,
during the time that the device is held in a power down state via the tri-state driver, the system would have
to ignore the interrupt signal from the device.
3.2
Configuration During Power Down Mode
In Power Down mode, the data path is disabled, that is, no signals are driven onto the MII/RMII or the
TPTD+/- and TPRD+/- pairs. The device registers can still be configured. Link speed, LED options and
interrupt settings are all examples of register configurations.
The DP83848 retains the user selected configuration data upon powering up to a normal operating mode.
2
AN-1402 DP83848 - Single 10/100 Mb/s Ethernet Transceiver Initialization
During Power Down Mode
SNOA463A – September 2005 – Revised April 2013
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Copyright © 2005–2013, Texas Instruments Incorporated
Power Down Configuration Sequence
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Figure 1. Initialization Via Pull Down Resistor
Figure 2. Intitialization Via Tri-state Driver
Figure 3. Initialization Via Driver
3.3
Exit from Power Down Mode
After the device is configured as desired, the device can be brought out of the Power Down mode into the
normal operation in one of two ways:
• If Power Down Mode was established by asserting the PWR_DOWN/INT pin low via an external
control signal, the signal can simply be driven high or tri-stated.
• If Power Down Mode was established using a pull-down resistor, normal operating mode is achieved
via the dual functionality of the pin. In this case, the user must set the INT_OE bit in the MII Interrupt
Control Register, MICR (0x11). This will enable the pin as an interrupt output, thus disabling the power
down input and allowing the device to enter a normal operating mode. Note that the pin should not be
utilized as a system interrupt in this case as the pull-down resistor would effectively signal a constant
interrupt.
SNOA463A – September 2005 – Revised April 2013
Submit Documentation Feedback
AN-1402 DP83848 - Single 10/100 Mb/s Ethernet Transceiver Initialization
During Power Down Mode
Copyright © 2005–2013, Texas Instruments Incorporated
3
Summary
4
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Summary
The DP83848 features an externally selectable option to enable Power Down mode. The device retains
register configuration while transitioning between power down mode and normal operation mode.
For systems or applications that are power conscious, the DP83848 is a perfect fit. In addition to an
architecture optimized for low power consumption, the DP83848 provides options for flexible device
configuration with minimal system intervention overhead.
4
AN-1402 DP83848 - Single 10/100 Mb/s Ethernet Transceiver Initialization
During Power Down Mode
SNOA463A – September 2005 – Revised April 2013
Submit Documentation Feedback
Copyright © 2005–2013, Texas Instruments Incorporated
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