Address Checking Block - Sharp LH79524 User Manual

LH79524/LH79525 User's Guide
If either NETCTL:
will be transmitted only if full duplex is selected in the NETCONFIG register, and transmit
is enabled in the NETCTL register. Pause frame transmission occurs immediately if trans-
mit is inactive or if transmit is active between the current frame and the next frame due to
be transmitted. The transmitted pause frame comprises:
• A destination address of 0x0180C2000001
• The MAC Source Address taken from the SPECAD1TOP and SPECAD1BOT registers
• A Type ID of 0x8808 (MAC control frame)
• A Pause Opcode of 0x0001
• A Pause Quantum
• The remaining bytes filled with 0x00 to make the frame length equal to required
minimum frame length (60 bytes)
• Valid FCS.
The Pause Quantum for the generated frame depends on the trigger source for the frame:
1. If NETCTL:TXPFRAME is programmed to 1, the pause quantum comes from the
TXPAUSEQ register. The TXPAUSEQ register resets to a value of 0xFFFF, giving a
maximum pause quantum as default.
2. If NETCTL:TXZEROQ is programmed to 1, the pause quantum will be zero.
After transmission, no interrupts are generated and the only statistics register incremented
is the TXPAUSEFM register.
Pause frames can also be transmitted by the MAC using normal frame transmission
methods. A pause frame can be sent while the transmitter is paused by resetting the
NETCONFIG:PAUSEEN bit.

6.1.5 Address Checking Block

The Address Checking Block examines the destination addresses of received frames and
indicates to the DMA Block which frames should be copied to memory
is copied depends on the Network Configuration register, the contents of the Specific
Address and Hash registers, and the frame's destination address.
If the NETCONFIG:ENFRM bit is 0, a frame received while the EMAC is transmitting in
half-duplex mode will not be copied to memory. If the NETCONFIG:ENFRM bit is 1, frames
can be received while transmitting in half-duplex mode.
Special Ethernet frames are also detected by the Address Checking block. Ethernet
frames are transmitted one byte at a time, least significant bit first. The first six bytes of an
Ethernet frame contains the destination address. The first bit of that destination address is
the group/individual bit: 1 for Multicast addresses and 0 for Unicast. The address
0xFFFFFFFFFFFF is the Broadcast address, a special case of Multicast.
The EMAC supports recognition of four specific addresses. Each specific address requires
two registers. Specific Address Register Bottom (SPECADxBOT) stores the first four bytes
of the address and Specific Address Register Top (SPECADxTOP) contains the last two
bytes. The addresses stored can be specific, group, local or universal. SPECAD1 should
be used for the MAC address.
TXZEROQ or NETCTL:TXPAUSEFM
Version 1.0
Ethernet MAC Controller
is programmed to 1, a pause frame
Whether a frame
.
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