Texas Instruments TMS320DM36X manual Industry Standards Compliance Statement, Clock Control

Models: TMS320DM36X

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Architecture

The EMAC and MDIO interrupts are combined within the control module, so only the control module interrupt needs to be monitored by the application software or device driver. The EMAC control module combines the EMAC and MDIO interrupts and generates 4 separate interrupts to the ARM through the ARM interrupt controller. See Section 2.17.4 for details of interrupt multiplex logic of the EMAC control module.

1.4Industry Standard(s) Compliance Statement

The EMAC peripheral conforms to the IEEE 802.3 standard, describing the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer specifications. The IEEE 802.3 standard has also been adopted by ISO/IEC and re-designated as ISO/IEC 8802-3:2000(E).

In difference from this standard, the EMAC peripheral does not use the Transmit Coding Error signal MTXER. Instead of driving the error pin when an underflow condition occurs on a transmitted frame, the EMAC intentionally generates an incorrect checksum by inverting the frame CRC, so that the transmitted frame is detected as an error by the network.

2Architecture

This section discusses the architecture and basic function of the EMAC/MDIO module.

2.1Clock Control

The frequencies for the transmit and receive clocks are fixed by the IEEE 802.3 specification as:

2.5 MHz at 10 Mbps

25 MHz at 100 Mbps

All EMAC logic is clocked synchronously with the PLL peripheral clock. The MDIO clock can be controlled through the application software, by programming the divide-down factor in the MDIO control register (CONTROL).

2.1.1MII Clocking

The transmit and receive clock sources are provided from an external PHY via the EMAC_TX_CLK and EMAC_RX_CLK pins. These clocks are inputs to the EMAC module and operate at 2.5 MHz in 10 Mbps mode and at 25 MHz in 100 Mbps mode. For timing purposes, data is transmitted and received with reference to EMAC_TX_CLK and EMAC_RX_CLK, respectively.

SPRUFI5B –March 2009 –Revised December 2010 Ethernet Media Access Controller (EMAC)/Management Data Input/Output 15

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Texas Instruments TMS320DM36X manual Industry Standards Compliance Statement, Clock Control, MII Clocking