Digilent chipKIT Network Shield Справочное руководство и руководство пользователя - Страница 4
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Печатать страницуchipKIT Network Shield Reference Manual
chipKIT Network Shield Hardware Description
Introduction
The following describes the hardware provided
by the Network Shield and its use. Appendices
at the end provide pin-out and connection
tables.
The Network Shield is designed to be used
with the chipKIT Max32 board. When used in
combination, the two boards provide the
necessary supporting hardware and
connectors to make use of all of the advanced
communications and networking features of
the PIC32MX795F512L microcontroller on the
Max32.
Ethernet Interface
The Network Shield provides the ability to
interface with 10Mbps or 100Mbps Ethernet
networks. The PIC32MX795 microcontroller on
the chipKIT Max32 board contains a 10/100
Ethernet Medium Access Controller (MAC).
The Network Shield provides an SMSC
LAN8720 Ethernet Physical Layer Transceiver
(PHY). Together, the MAC and PHY provide a
complete 10/100 Ethernet interface.
The RJ45 connector, J1, provides the physical
connection to an Ethernet network using a
standard Ethernet cable.
When the Ethernet controller is enabled in the
PIC32 microcontroller, it takes over the use of
a number of the microcontroller pins. All of the
signals from these pins are taken from
connector J10 on the Network Shield
(connector J8 on the Max32). Three of these
signals are also shared with connector J7 on
the Max32 and are analog pins A11, A12, and
A13. When the Ethernet interface on the
Network Shield is being used, these pins are
not available for other use, and nothing should
be connected to them to avoid interference
with the operation of the Ethernet interface.
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All devices on an Ethernet network must have
a unique address. This address is used to
direct packets on the network to a specific
device and to identify the device that originated
a packet. An Ethernet MAC uses a 48-bit
address value, commonly called the 'MAC
Address'. These address values are globally
unique to ensure that no two devices on a
network can have conflicting addresses. MAC
addresses are assigned by the IEEE. The
address to use with the Network Shield is
printed on a sticker attached to the bottom of
the board. The address is a twelve digit
hexadecimal number of the form:
00183Exxxxxx, where xxxxxx represents six
hexadecimal digits. This value is used to
initialize the Ethernet Controller MAC Station
Address registers in the Ethernet controller of
the PIC32MX795 microcontroller.
In order to connect to and operate with an
Ethernet network, the PIC32 microcontroller
must be running network protocol stack
firmware. Normally, the TCP/IP (Transmission
Control Protocol/Internet Protocol) network
protocol is used and "TCP/IP Stack" software
will be used. The Ethernet library provided for
use with the Network Shield board provides the
necessary stack support for use of the chipKIT
Max32/Network Shield from within the MPIDE
programming environment.
If the board is being used outside the MPIDE
programming environment, The Microchip
Applications Library, available for download
from the Microchip web site provides full
protocol stack support compatible with the
PIC32MX795 MAC and the LAN8720 PHY.
Microchip also provides numerous example
programs illustrating the use of their network
protocol stack for various applications.
When not using the either the chipKIT Ethernet
library or the Microchip network protocol stack,
refer to the manufacturer documentation for
the PIC32MX795 and LAN8720, plus network
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