MC68EN302AG25BT

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1. Describe

Freescale has introduced a version of the well-known MC68302 Integrated Multi-Protocol Processor (IMP) with Ethernet and DRAM controller. It is called the MC68EN302 and extends the family of devices based on the MC68302. The Ethernet controller has a 16-bit interface on the 68000 bus and provides full IEEE 802.3 compatibility. The programming model adopts the standard 68302 programming model. DRAM controller adopts MC68306 product. It is enhanced to support parity and external bus masters. The MC68EN302 is available in a low profile 144 TQFP package. The Ethernet controller consists of the Ethernet protocol core, transmit and receive FIFOs, and a 16-bit wide data/control interface connected to the 68000 bus. The Ethernet Protocol Core (EPC) provides compatibility with the IEEE 802.3 Ethernet standard. Transmit and receive FIFOs allow the EPC to automatically handle collisions and collision fragments, and they also provide bus latency that a DMA channel may encounter. Separate DMA channels are used for transmit and receive data paths. Dual-port RAM is used for on-chip buffer descriptors. The Buffer Descriptor Control (BDC) block updates buffer descriptors. The control status register is used to directly control all modules in the Ethernet controller.

2. Feature

    1. Does not affect the performance of existing SCCs

    2. 802.3 MAC layer support

    3. Compatible with 68160 EEST (twisted pair/AUI)

    4. Two dedicated Ethernet DMA channels, transmit and receive

    5. Full duplex (switched) Ethernet support

    6. Up to 10 Mb/s operating speed (20 Mb/s full duplex)

    7. 128-byte FIFO for transmit and receive

    8. No CPU or bus overhead on Rx or Tx frame collisions

    9. 64-item CAM with hash option

  10. 128 internal buffer descriptors

  11. Execute framework functions

  12. Full collision support

  13. Receive back-to-back frames

  14. Detection of overly long received frames

  15. Multi-buffer data structures

  16. Supports 48-bit addressing

  17. Heartbeat indication

  18. Transmitter network management and diagnostics

  19. Receiver network management and diagnostics

  20. Loopback mode for testing

  21. Non-aggressive deferral options

  22. Heartbeat status and interrupt options

  23. Graceful stop command

3. Memory controller

    1. Provides two CAS lines

    2. Provides two RAS lines (supports two banks)

    3. DRAM address multiplexing on standard address bus

    4. Programmable up to three wait states

    5. 100 nS DRAM for zero wait states at 20 MHz

    6. 80 nS DRAM for zero wait states at 25 MHz

    7. CAS before RAS refresh and refresh support during system reset

    8. Programmable refresh and precharge cycles

    9. RAS line separated from four chip selects

  10. Access hidden refreshes from the bus

  11. Write protection option

  12. Programmable size of each bank from 128Kbytes to 8Mbytes

4. Application

The MC68EN302 is suitable for low-end bridge and router applications. it has three SCCs The MC68302, plus an additional Ethernet interface, has a total of four serial interfaces. Since the MC68EN302 has three SCCs as well as an Ethernet interface, it would be an excellent Choice of ISDN to Ethernet routers. For remote access dial-up, the MC68EN302 can be used with a dial-up modem that will connect to Ethernet LAN.