Freescale Semiconductor POWERPC MPC860T - Manual (Page 14)

1-4 MPC860T (Rev. D) Fast Ethernet Controller Supplement MOTOROLA
PRELIMINARYÑSUBJECT TO CHANGE WITHOUT NOTICE
Figure 1-1. MPC860T Block Diagram
The FEC complies with the IEEE 802.3 speciÞcation for 10- and 100-Mbps connectivity.
Full-duplex 100-Mbps operation is supported at system clock rates of 40 MHz and higher.
A 25-MHz system clock supports 10-Mbps operation or half-duplex 100-Mbps operation.
The implementation of bursting DMA reduces bus usage. Independent DMA channels for
accessing BDs and transmit and receive data minimize latency and FIFO depth
requirements.
Transmit and receive FIFOs further reduce bus usage by localizing all collisions to the FEC.
Transmit FIFOs maintain a full collision window of transmit frame data, eliminating the
need for repeated DMA over the system bus when collisions occur. On the receive side, a
full collision window of data is received before any receive data is transferred into system
memory, allowing the FIFO to be ßushed in the event of a runt or collided frame, with no
DMA activity. However, external memory for buffers and BDs is required; on-chip FIFOs
are designed only to compensate for collisions and for system bus latency.
Independent TxBD and RxBD rings in external memory allow nearly unlimited ßexibility
Bus
System Interface Unit (SIU)
Embedded
Parallel I/O
Memory Controller
4 Timers
Interrupt
Controllers
Dual-Port RAM
Serial
and
System Functions
Real-Time Clock
PCMCIA-ATA Interface
4-KByte
Instruction MMU
Data MMU
Instruction
Bus
Load/Store
Bus
Unified
Baud Rate
Generators
Parallel Interface Port
and UTOPIA
MAC
Internal
Bus Interface
Unit
External
Bus Interface
Unit
Timers
32-Bit RISC Controller
and Program
ROM
Serial Interface
I
2
C SPI
Time Slot Assigner
PowerPC
Processor
Core
DMAs
FIFOs
10/100
MII
Base-T
Media Access
Serial Interface
I
2
C SPI
Time Slot Assigner
Control
DMA
Channels
Fast
Ethernet
Controller
Instruction Cache
4-KByte
Data Cache
SCC1 SCC2 SCC3 SCC4 SMC1 SMC2
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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