SMSC LAN9312 - Manual (Page 25)

High Performance Two Port 10/100 Managed Ethernet Switch with 32-Bit Non-PCI CPU Interface
Datasheet
SMSC LAN9312 25 Revision 1.4 (08-19-08)
DATASHEET
2.2.9 GPIO/LED Controller
The LAN9312 provides 12 configurable general-purpose input/output pins which are controlled via this
module. These pins can be individually configured via the GPIO/LED CSRs to function as inputs, push-
pull outputs, or open drain outputs and each is capable of interrupt generation with configurable
polarity. Two of the GPIO pins (GPIO[9:8]) can be used for IEEE 1588 timestamp functions, allowing
GPIO driven 1588 time clock capture when configured as an input, or GPIO output generation based
on an IEEE 1588 clock target compare event.
In addition, 8 of the GPIO pins can be alternatively configured as LED outputs. These pins, GPIO[7:0]
(nP1LED[3:0] and nP2LED[3:0]), may be enabled to drive Ethernet status LEDs for external indication
of various attributes of the switch ports.
2.3 System Configuration
In a typical application, the LAN9312 Host Bus Interface (HBI) is connected to the host
microprocessor/microcontroller via the asynchronous 32-bit interface, allowing access to the LAN9312
system configuration and status registers. The LAN9312 utilizes the internal Host MAC to provide a
network path for the host CPU. The LAN9312 may share the host bus with additional system memory
and/or peripherals. For more information on the HBI, refer to
Chapter 8, "Host Bus Interface (HBI)," on
page 99 .
The 2 Ethernet ports of the LAN9312 must be connected to Auto-MDIX style magnetics for proper
operation on the Ethernet network. Refer to the SMSC Application Note 8.13 “Suggested Magnetics”
for further details.
The LAN9312 also supports optional EEPROM and GPIOs/LEDs. When an EEPROM is connected,
the EEPROM loader can be used to load the initial device configuration from the external EEPROM
via the I
2
C/Microwire interface.
A system configuration diagram of the LAN9312 in a typical embedded environment can be seen in
Figure 2.2 .
Figure 2.2 System Block Diagram
Magnetics
Magnetics
To Ethernet
To Ethernet
External
25MHz Crystal
Microprocessor/
Microcontroller
GPIOs/LEDs
(optional)
System
Memory
System
Peripherals
EEPROM
(optional)
LAN9312
I 2 C/Microwire