Programming the Ethernet controller

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Interface

See also: Ethernet packets
See also: Ethernet state diagram

Emulator

Controller

  • transceiver
    • This block provides a level of abstraction between the precise CP2200/1 interface and a generalized interface seen by the internal blocks of the FPGA. It takes information on the next transfer to carry out and returns information on the last transfer completed. It has a pulse signal to begin a transfer and a pulse signal to notify of a completed transfer. This eliminates a need for the internal workings of the FPGA to be aware of the timing of the interface; it simply begins a transfer and waits for notification of the transfer's completion.
    • inputs
      • CLK: clock
      • /Rst: asynchronous, active-low reset
      • Go: pulse to begin a transmission
      • R/W_in: read/write toggle: active-high read, active-low write
      • A_in: 8-bit bus for address to read to/write from
      • D_in: 8-bit bus for data to write; ignored during a read
    • outputs to internals
      • Done: pulse to signal completion of a transmission
      • R/W_out: read/write flag: active-high read, active-low write
      • A_out: 8-bit bus for address of last read/write
      • D_out: 8-bit bus for data of last read; internal systems should ignore for a write
    • outputs to CP2200/1
      • /CS: active-low chip select
      • MotEn: Motorola/Intel format toggle: active-high Motorola, active-low Intel
      • MuxEn: Multiplexed flag; not used for CP2201
      • ALE: ALE strobe
      • /Wr: Active-low write flag
      • /Rd: Active-low read flag
    • inouts
      • AD: 8-bit address and data bus

(000) Reset Cycle

inputs

  • Clk: clock
  • /Rst: asynchronous, active-low reset
  • State: 3-bit state value
  • D_En: DAC enable, assume held high/low by previous block
  • A_En: ADC enable, assume held high/low by previous block
  • E_En: Ethernet enable, assume held high/low by previous block

internal signals

  • S_En: state enable, S_En <= not (St(2) or St(1) or St(0))
  • Go: when S_En goes high Go pulses for one cycle
  • D_Go: DAC reset go pulse, D_Go <= Go and D_En
  • A_Go: ADC reset go pulse, A_Go <= Go and A_En
  • E_Go: Ethernet reset go pulse, E_Go <= Go and E_En

blocks

  • DAC Reset
    • Resets and initializes the DAC.
    • inputs
      • Clk: clock
      • /Rst: asynchronous, active-low reset
      • D_Go: go pulse to begin reset/initialization process
    • outputs
      • - All DAC reset/initialization control lines -
      • D_Done: goes high when reset/initialization process is complete, falls on D_Go pulse
  • ADC Reset
    • Resets and initializes the ADC.
    • inputs
      • Clk: clock
      • /Rst: asynchronous, active-low reset
      • A_Go: go pulse to begin reset/initialization process
    • outputs
      • - All ADC reset/initialization control lines -
      • A_Done: goes high when reset/initialization process is complete, falls on A_Go pulse
  • Ethernet Reset
    • Resets and initializes the Ethernet controller.
    • inputs
      • Clk: clock
      • /Rst: asynchronous, active-low reset
      • E_Go: go pulse to begin reset/initialization process
    • outputs
      • - All Ethernet reset/initialization control lines -
      • E_Done: goes high when reset/initialization process is complete, falls on E_Go pulse
  • Coordinator
    • Coordinates the completion of each reset cycle and notifies other blocks that the reset process is complete.
    • inputs
      • Clk: clock
      • /Rst: asynchronous, active-low reset
      • D_En: high when DAC is to be reset
      • D_Done: high when DAC is done resetting
      • A_En: high when ADC is to be reset
      • A_Done: high when ADC is done resetting
      • E_En: high when Ethernet controller is to be reset
      • E_Done: high when Ethernet controller is done resetting
    • internal signals
      • Flag <= (D_Done or not D_En) and (A_Done or not A_En) and (E_Done or not E_En)
    • outputs
      • Done: when Flag goes high, Done pulses for one cycle; connects to state counter as an enable (thereby incrementing the State to 001)

(001) Transmit "I"

(010) Idle

(011) Read Packet

(100) Poll Status

(101) Transmit "S"

(110) Program DAC

(111) Transmit "D"