UM0851 datasheet(55/245 Pages) STMICROELECTRONICS

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UM0851

Communication device drivers

Doc ID 16604 Rev 2

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Other miscellaneous options:

4.2

MACB (MAC block) driver

MACB is a 10M/100M Ethernet controller, with an SMII (Serial MII) interface to an external

PHY. This section describes the driver for MACB Ethernet controller embedded in SPEAr.

The IP is provided by Cadence.

4.2.1

Hardware overview

The MACB module implements a 10/100 Ethernet MAC compatible with the IEEE 802.3

standard using an address checker, statistics and control registers, as well as receive and

transmit blocks and a DMA interface. The address checker recognizes four specific 48-bit

addresses and contains a 64-bit hash register for matching multicast and unicast addresses.

It can recognize the broadcast address of all ones, copy all frames, and act on an external

address match signal.

Table 17.

Other options

Configuration option

Comment

JUMBO frame size

Can be configured by setting ifconfig eth0 mtu <size>.

CRC_OFFLOAD

Checksum offloading is used to relieve the kernel (and

thus the CPU) from the burden of calculating transport-

PDU checksums (TCP and UDP checksums) when the

SPEAr MAC hardware can perform these calculations

itself.

No of receive/ transmit descriptors

Setup the number of DMA descriptors being used in

reception and transmission. The default has been set to

32 for both reception and transmission.

ETH_SPEAR_CRC_STRIP

This option enables the GMAC to strip the PAD/FCS on

the incoming frames only when the length of the frame

is less than or equal to 1500 bytes.

Ethtool

Ethtool is used for querying the settings of an Ethernet

device and changing them.

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