EMAC
control
module
Control
registers
and logic
PHY
monitoring
Peripheral
clock
MDIO
clock
generator
USERINT
MDIO
interface
polling
PHY
MDCLK
MDIO
LINKINT
Configuration bus
Architecture
1828
SPNU563A – March 2018
Copyright © 2018, Texas Instruments Incorporated
EMAC/MDIO Module
32.2.7.3 Bus Arbiter
The EMAC control module bus arbiter operates transparently to the rest of the system. It is used:
•
To arbitrate between the CPU and EMAC buses for access to internal descriptor memory.
•
To arbitrate between internal EMAC buses for access to system memory.
32.2.8 MDIO Module
The MDIO module is used to manage up to 32 physical layer (PHY) devices connected to the Ethernet
Media Access Controller (EMAC). The device supports a single PHY being connected to the EMAC at any
given time. The MDIO module is designed to allow almost transparent operation of the MDIO interface
with little maintenance from the CPU.
The MDIO module continuously polls 32 MDIO addresses in order to enumerate all PHY devices in the
system. Once a PHY device has been detected, the MDIO module reads the MDIO PHY link status
register (LINK) to monitor the PHY link state. Link change events are stored in the MDIO module, which
can interrupt the CPU. This storing of the events allows the CPU to poll the link status of the PHY device
without continuously performing MDIO module accesses. However, when the CPU must access the MDIO
module for configuration and negotiation, the MDIO module performs the MDIO read or write operation
independent of the CPU. This independent operation allows the processor to poll for completion or
interrupt the CPU once the operation has completed.
The MDIO module does not support the "Clause 45" interface.
32.2.8.1 MDIO Module Components
The MDIO module (
) interfaces to the PHY components through two MDIO pins (MDIO_CLK
and MDIO), and to the CPU through the EMAC control module and the configuration bus. The MDIO
module consists of the following logical components:
•
MDIO clock generator
•
Global PHY detection and link state monitoring
•
Active PHY monitoring
•
PHY register user access
Figure 32-13. MDIO Module Block Diagram