Functional Description
929
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Ethernet Controller
2. Disable the MAC transmit and receive state machine by clearing the TE and RE bits in the Ethernet
MAC Configuration (EMACCFG) register.
3. Wait until the RX DMA empties all the frames from the Rx FIFO to system memory by polling the RXF
field of the Ethernet MAC Status (EMACSTATUS) register.
4. Enable a power management mode by setting the magic packet, global unicast or remote wake-up
enable bit in the EMACPMTCTLSTAT register.
5. Enable the MAC receive state machine in the EMACCFG register and enter the Power-Down mode by
setting the PWRDWN bit in the EMACPMTCTLSTAT register.
6. On receiving a valid remote wake-up frame, the PMT interrupt is set in the EMACRIS register and the
Ethernet MAC exits the Power-Down mode.
7. Read the EMACPMTCTLSTAT register to clear the PMT interrupt, then enable the other modules in
the system and resume normal operation.
15.3.12 Serial Management Interface
The Ethernet MAC has the ability to read or write to the PHY registers through the EN0MDIO and
EN0MDC signals of the Serial Management Interface defined by the IEEE 802.3 standard. The internal
EN0MDIO and EN0MDC signals connect to the integrated PHY as well as to the external EN0MDIO and
EN0MDC pins. The EN0MDC signal is a 2.5-MHz clock that is sourced from System Clock (SYSCLK) and
then divided down to the required frequency by programming the CR field in the Ethernet MAC MII
Address (EMACMIIADDR) register. To access the integrated PHY, the PLA field in the EMACMIIADDR
register must be 0x0. The available addresses for external PHYs are 0x01 to 0x1F.
15.3.13 Reduced Media Independent Interface (RMII)
The Reduced Media Independent Interface (RMII) specification reduces the pin count between Ethernet
PHYs and Ethernet MACs. According to the IEEE 802.3u standard, an MII contains 16 pins for data and
control. In devices incorporating multiple MAC or PHY interfaces such as switches, the number of pins
adds significant cost with increase in port count. The RMII specification addresses this problem by
reducing the pin count to 7 for each port — a 62.5% decrease in pin count.
The RMII module has the following features:
•
Supports both 10-Mbps and 100-Mbps operating rates
•
Provides independent, two-bit wide transmit and receive paths
Each nibble is transmitted on the RMII two bits at a time. For a nibble {D3, D2, D1, D0}, the data is
transferred as {D1, D0} followed by {D3, D2}.
15.3.14 Interrupt Configuration
Interrupts can be generated from the MAC as a result of various events in the MAC and submodules.
MAC interrupts are enabled or disabled in the Ethernet MAC Interrupt Mask (EMACIM) register, MAC
offset 0x03C. Each interrupt event can be masked by setting the corresponding mask bit in the EMACIM
register.
The interrupt register bits in the Ethernet MAC Raw Interrupt Status (EMACRIS) register only indicate the
submodule from which the event is reported. The application must read the corresponding status registers
to clear the interrupt.
15.4 Ethernet PHY
The integrated PHY supports 10Base-T and 100Base-TX signaling. It integrates all the physical-layer
functions needed to transmit and receive data on standard twisted-pair cables. The PHY directly interfaces
to the integrated Media Access Controller (MAC).
The Ethernet PHY uses mixed-signal processing to perform equalization, data recovery, and error
correction to achieve robust operation over CAT5 twisted-pair wiring. It not only meets the requirements of
IEEE 802.3, but maintains high margins in terms of alien cross-talk. The following highlights the features
of the PHY module:
•
Cable Diagnostics