Datasheet
Table Of Contents
- Small Footprint RMII 10/100 Ethernet Transceiver with HP Auto-MDIX Support
- 1.0 Introduction
- 2.0 Pin Description and Configuration
- 3.0 Functional Description
- 3.1 Transceiver
- 3.2 Auto-negotiation
- 3.3 HP Auto-MDIX Support
- 3.4 MAC Interface
- 3.5 Serial Management Interface (SMI)
- 3.6 Interrupt Management
- 3.7 Configuration Straps
- 3.8 Miscellaneous Functions
- 3.9 Application Diagrams
- 4.0 Register Descriptions
- 4.1 Register Nomenclature
- 4.2 Control and Status Registers
- TABLE 4-2: SMI Register Map
- 4.2.1 Basic Control Register
- 4.2.2 Basic Status Register
- 4.2.3 PHY Identifier 1 Register
- 4.2.4 PHY Identifier 2 Register
- 4.2.5 Auto Negotiation Advertisement Register
- 4.2.6 Auto Negotiation Link Partner Ability Register
- 4.2.7 Auto Negotiation Expansion Register
- 4.2.8 Mode Control/Status Register
- 4.2.9 Special Modes Register
- 4.2.10 Symbol Error Counter Register
- 4.2.11 Special Control/Status Indications Register
- 4.2.12 Interrupt Source Flag Register
- 4.2.13 Interrupt Mask Register
- 4.2.14 PHY Special Control/Status Register
- 5.0 Operational Characteristics
- 6.0 Package Information
- 7.0 Application Notes
- Appendix A: Data Sheet Revision History
- The Microchip Web Site
- Customer Change Notification Service
- Customer Support
- Product Identification System
- Worldwide Sales and Service
FIGURE 3-8: SOURCING REF_CLK FROM A 25MHZ CRYSTAL
LAN8720A/LAN8720Ai
10/100 PHY
24-QFN
RMII
TXP
TXN
Mag RJ45
RXP
RXN
25MHz
XTAL1/CLKIN
XTAL2
LED[2:1]
2
Interface
nRST
TXD[1:0]
2
RXD[1:0]
CRS_DV
2
RMII
MDIO
MDC
TXEN
REFCLKO
MAC
Capable of
accepting 50MHz
clock
Note: nINT not available in
this configuration
RXER
REF_CLK
LAN8720A/LAN8720AI
DS00002165B-page 30 2016 Microchip Technology Inc.
In some system architectures, a 25MHz clock source is available. The device can be used to generate the REF_CLK
to the MAC as shown in FIGURE 3-9:. It is important to note that in this speci
fic example, only a 25MHz clock can be
used (clock cannot be 50MHz). Similar to the 25MHz crystal mode, the nINT function is disabled.