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
LAN8720A/LAN8720AI
DS00002165B-page 32 2016 Microchip Technology Inc.
3.8.1.1 REGOFF and LED1 Polarity Selection
The REGOFF configuration strap is shared with the LED1 pin. The LED1 output will automatically change polarity based
on the presence of an external pull-up resistor. If the LED1 pin is pulled high to VDD2A by an external pull-up resistor
to select a logical high for
REGOFF, then the LED1 output will be active low. If the LED1 pin is pulled low by the internal
pull-down resistor to select a logical low for REGOFF, the LED1 output will then be an active high output. Figure 3-7
details the LED1 polarity for each
REGOFF configuration.
FIGURE 3-10: LED1/REGOFF POLARITY CONFIGURATION
LED1/REGOFF
~270 ohms
REGOFF
= 0 (Regulator ON)
LED output = Active High
~270 ohms
VDD2A
REGOFF
= 1 (Regulator OFF)
LED output = Active Low
LED1/REGOFF
10K
Note: Refer to Section 3.7.4, "REGOFF: Internal +1.2V Regulator Configuration," on page 32 for additional infor-
mation on the REGOFF configuration strap.
3.8.1.2 nINTSEL and LED2 Polarity Selection
The nINTSEL configuration strap is shared with the LED2 pin. The LED2 output will automatically change polarity based
on the presence of an external pull-down resistor. If the LED2 pin is pulled high to VDD2A to select a logical high for
nINTSEL, then the LED2 output will be active low. If the LED2 pin is pulled low by an external pull-down resistor to select
a logical low for nINTSEL, the LED2 output will then be an active high output. Figure 3-8 details the LED2 polarity for
each nINTSEL configuration.
FIGURE 3-11: LED2/NINTSEL POLARITY CONFIGURATION
~270 ohms
nINTSEL
= 0
LED output = Active High
10K
~270 ohms
VDD2A
nINTSEL
= 1
LED output = Active Low
LED2/nINTSEL
LED2/nINTSEL
Note: Refer to Section 3.7.5, "nINTSEL: nINT/TXER/TXD4 Configuration," on page 32 for additional information
on the
nINTSEL configuration strap.