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6.18.2 Interrupt Controller and Pacing Interrupts

TMS320DM647/TMS320DM648

Digital Media Processor

SPRS372A – MAY 2007 – REVISED JUNE 2007

• Transmit operations are initiated by C64x+ DSP writes to the appropriate transmit channel head

descriptor pointer contained in the CPDMA block. The CPDMA TX controller then fetches the first

packet in the packet chain from memory in accordance with the CPPI protocol for the GMAC to

process before sending to the SGMII.

• Receive operations are initiated by C64x+ DSP writes to the appropriate receive channel head

descriptor pointer. The CPDMA RX controller then writes packets to memory in accordance with the

CPPI protocol.

DSP writes may be write-protected to the Ethernet Subsystem configuration registers from addresses

0x02D0 0000 – 0x02D0 4FFF (3PGSW, MDIO, SGMII0, SGMII1, control), and the CPPI RAM. The

Ethernet Subsystem setting in the PSC is also write-protected. A specific 32-bit lock code and a 32-bit

unlock code written to ESS_LOCK register will activate or clear this option, respectively.Please see

section Section 3.2.5 and section Section 3.2.8

The 3-port gigabit switch block contains the following functions:

• 3-port gigabit switch: performs packet forwarding and routing functions, one port is internally connected

to the C64x+ DSP and two ports are brought out externally

• CPDMA: performs high-speed DMA transfers with RX and TX CPPI buffers in local memory, including

channel setup and channel teardown

• GMAC (Gigabit Ethernet MAC):

–

Uses Rx packet FIFO, and a TX packet FIFO to improve data transfer efficiency

–

Handles processing of Ethernet packet data, frames, and headers

–

Includes flow control

–

Provides statistics collection and reporting

• The address lookup engine (ALE) processes all received packets to determine where (that is, which

packet location) to forward the packet. The ALE uses the incoming packet received port number,

destination address, source address, length/type, and VLAN information to determine how the packet

should be forwarded. The ALE outputs the port mask to the switch fabric that indicates to which packet

the port(s) should be forwarded.

The interrupt control block selects the interrupts from the 3-port gigabit switch and MDIO modules for

output to the C64x+ DSP. The miscellaneous interrupt is an immediate (non-paced) interrupt selected

from the miscellaneous interrupts (host error level, statistics level, MDIO User [2], MDIO link [2]).

The eight RX interrupts and eight TX interrupts can be paced. The 8 RX threshold interrupts and the

miscellaneous interrupts are not paced. The interrupt pacing feature limits the number of interrupts that

occur during a given period of time. For heavily loaded systems in which interrupts can occur at a very

high rate, the performance benefit is significant due to minimizing the overhead associated with servicing

each interrupt. Interrupt pacing increases the C64x+ DSP cache hit ratio by minimizing the number of

times that large interrupt service routines are moved to and from the DSP instruction cache.

MDIO

The MDIO module manages the PHY configuration and monitors status. For a list of supported registers

and register fields, see Table 6-65. In 10/100 mode, the GMII_MTXD(7:0) data bus uses only the lower

nibble.

SGMII

The SGMII/SerDes module contains:

• Gigabit differential current mode logic (CML) receiver/transmitters

• An integrated RX/TX PLL to provide the required high-quality/high-speed internal clocks

• Phase-interpolator-based clock/data recovery

• A bandgap reference for transmitter swing settings

Peripheral Information and Electrical Specifications

144

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