'buffer boundaries applied to internal 8K ram
 'entire available packet buffer space is allocated
 Txstart_init  =  0x1800  ' start TX buffer at 0
 Rxstart_init  =  0x0000  ' give TX buffer space for one full ethernet frame (~1500 bytes)
 Rxstop_init   =  0x17FE  ' receive buffer gets the rest

...


Sub Enc28j60init()

    NextPacketPointer = Rxstart_init

    'do bank 0 stuff
    'initialize receive buffer
    '16-bit transfers, must write low byte first
    'set receive buffer start address
    Value = Low(Rxstart_init)
    Enc28j60writecontrolregbyte(Erxstl , Value)
    Value = High(Rxstart_init)
    Enc28j60writecontrolregbyte(Erxsth , Value)
    'set receive pointer address
    Value = Low(Rxstart_init)
    Enc28j60writecontrolregbyte(Erxrdptl , Value)
    Value = High(Rxstart_init)
    Enc28j60writecontrolregbyte(Erxrdpth , Value)
    'set receive buffer end
    Value = Low(Rxstop_init)
    Enc28j60writecontrolregbyte(Erxndl , Value)
    Value = High(Rxstop_init)
    Enc28j60writecontrolregbyte(Erxndh , Value)
    'set transmit buffer start
    Value = Low(Txstart_init)
    Enc28j60writecontrolregbyte(Etxstl , Value)
    Value = High(Txstart_init)
    Enc28j60writecontrolregbyte(Etxsth , Value)
    'do bank 2 stuff
    'enable MAC receive
    Value = 0
    'Value.macon1_marxen = 1
    Value = set_Bit_in_Byte(Value,Macon1_marxen,1)
    'Value.macon1_txpaus = 1
    Value = set_Bit_in_Byte(Value,Macon1_txpaus,1)
    'Value.macon1_rxpaus = 1
    Value = set_Bit_in_Byte(Value,Macon1_txpaus,1)

    Enc28j60writecontrolregbyte(Macon1 , Value)
    'bring MAC out of reset
    'enable automatic padding and CRC operations
    Value = 0
    'Value.Macon3_padcfg0 = 1
    Value = set_Bit_in_Byte(Value,Macon3_padcfg0,1)
    'Value.Macon3_txcrcen = 1
    Value = set_Bit_in_Byte(Value,Macon3_txcrcen,1)
    'Value.Macon3_frmlnen = 1
    Value = set_Bit_in_Byte(Value,Macon3_frmlnen,1)
    'Duplex  0=Halb 1=Full
    Value = set_Bit_in_Byte(Value,Macon3_fuldpx,0)

    Enc28j60writecontrolregbyte(Macon3 , Value)

    'set inter-frame gap (non-back-to-back)
    Enc28j60writecontrolregbyte(Maipgl , &H12)
    Enc28j60writecontrolregbyte(Maipgh , &H0C)
    'set inter-frame gap (back-to-back)
    Enc28j60writecontrolregbyte(Mabbipg , &H12)
    'set the maximum packet size which the controller will accept
    Value = Low(max_framelen)
    Enc28j60writecontrolregbyte(Mamxfll , Value)
    Value = High(max_framelen)
    Enc28j60writecontrolregbyte(Mamxflh , Value)

    'bank 3 stuff
    Enc28j60writecontrolregbyte(Maadr5 , Ethaddr0)
    Enc28j60writecontrolregbyte(Maadr4 , Ethaddr1)
    Enc28j60writecontrolregbyte(Maadr3 , Ethaddr2)
    Enc28j60writecontrolregbyte(Maadr2 , Ethaddr3)
    Enc28j60writecontrolregbyte(Maadr1 , Ethaddr4)
    Enc28j60writecontrolregbyte(Maadr0 , Ethaddr5)

    'no loopback of transmitted frames
    Enc28j60writephyword(Phcon2 , Phcon2_hdldis)
    'switch to bank 0
    Enc28j60selectbank(0)
    'enable interrupts
    Value = 0
    'Value.Eie_intie = 1
    Value = set_Bit_in_Byte(Value,Eie_intie,1)
    'Value.Eie_pktie = 1
    Value = set_Bit_in_Byte(Value,Eie_pktie,1)
    Enc28j60bitfield_set(Eie , Value)

    'enable packet reception
    Value = 0
    'Value.Econ1_rxen = 1
    Value = set_Bit_in_Byte(Value,Econ1_rxen,1)
    Enc28j60bitfield_set(Econ1 , Value)

End Sub




Sub Enc28j60packetreceive()
   Dim Wtemp As Word
   Dim Rxstat As Word
   Dim x_int As Integer
   Dim i As Integer

   'Reset Led
   'Print "EPKTCNT = " ; Bin(enc28j60_data)

   'set the read pointer to the start of the received packet
   Value = Low(NextPacketPointer)
   Enc28j60writecontrolregbyte(Erdptl , Value) 'Call
   Value = High(NextPacketPointer)
   Enc28j60writecontrolregbyte(Erdpth , Value) 'Call
   'Print "Present nextpacketpntr " ; Hex(nextpacketptr)

   'Enc28j60_cs = 0
   Port_WriteBit(13,1)   'PortB.5 = CS - SD Card  - 0 = selected Slave
   Port_WriteBit(14,0)   'PortB.6 = CS - ENC28J60 - 0 = selected Slave
   AbsDelay(1)

   'Send Read Buffer Memory command
   'Spdr = &H3A
   SPI_Write(&H3A)
   SPI_ReadBuf(Buffer,6)

   'Integer = MSB * 256 + LSB
   '1. Word
   NextPacketPointer = Buffer(1) * 256
   NextPacketPointer = NextPacketPointer + Buffer(0)

   '2. Word
   Length = Buffer(3) * 256
   Length = Length + Buffer(2)

   '3. Word
   Rxstat = Buffer(5) * 256
   Rxstat = Rxstat + Buffer(4)

   'Msg_WriteText("New Nextpacketpntr ")
   'Msg_WriteHex(Nextpacketptr)
   'Msg_WriteText("Packetlength = ")
   'Msg_WriteInt(Length)
   'Msg_WriteText("Rxstat = ")
   'Msg_WriteInt(Rxstat)

   'Get the payload
   Length = Length - 4                                     'Discard CRC

   SPI_ReadBuf(Buffer,Length)

   'Enc28j60_cs = 1
   Port_WriteBit(13,1)   'PortB.5 = CS - SD Card  - 0 = selected Slave
   Port_WriteBit(14,1)   'PortB.6 = CS - ENC28J60 - 0 = selected Slave

   'move the rx read pointer to the start of the next received packet
   'this frees the memory we just read out
   'Errata workaround #13, Packetpointer must Not contain even number
   If (NextPacketPointer - 1) >= Rxstop_init Then '0xFFFF Then
      'enc28j60Write(ERXRDPTL, LO(RXSTOP_INIT))
      'enc28j60Write(ERXRDPTH, HI(RXSTOP_INIT))
      Value = Low(Rxstop_init)
      Enc28j60writecontrolregbyte(Erxrdptl , Value) 'Call
      Value = High(Rxstop_init)
      Enc28j60writecontrolregbyte(Erxrdpth , Value) 'Call
      NextPacketPointer = Rxstop_init
   Else
      Value = Low(NextPacketPointer)
      Enc28j60writecontrolregbyte(Erxrdptl, Value)
      Value = High(NextPacketPointer)
      Enc28j60writecontrolregbyte(Erxrdpth, Value)
   End If

   'decrement the packet counter indicate we are done with this packet
  'enc28j60WriteOp(ENC28J60_BIT_FIELD_SET, ECON2, ECON2_PKTDEC)
  Enc28j60bitfield_set( Econ2, Econ2_pktdec)

   Value = Low(NextPacketPointer)
   Enc28j60writecontrolregbyte(Erxrdptl , Value) 'Call
   Value = High(NextPacketPointer)
   Enc28j60writecontrolregbyte(Erxrdpth , Value) 'Call


   'decrement the packet counter indicate we are done with this packet
   Value = 0
   Value = set_Bit_in_Byte(Value,Econ2_pktdec,1)
   Enc28j60bitfield_set(Econ2 , Value) 'Call





   'Set Led

   ''Print the packet content
    'Print "The packet:"
    'For X = 1 To Length
        'Print Hex(buffer(x)) ; "  " ;
    'Next 'X
    'Print

   ' Serial_Write(0,Ethernet_Packet_Count)
   ' Serial_Write(0,Length)
   ' For i = 0 To 60
   '     Serial_Write(0,Buffer(i))
   ' Next
      'Serial_Write(0,LF)

    'Handle the packet
    If Buffer(12) = &H08 Then
      If Buffer(13) = &H06 Then                             'Type:ARP
         If Buffer(20) = &H00 Then                          'ARP request
            If Buffer(21) = &H01 Then                       'ARP request
              If Buffer(38) = Ipaddr0 Then                  'ARP for us
                If Buffer(39) = Ipaddr1 Then
                   If Buffer(40) = Ipaddr2 Then
                      If Buffer(41) = Ipaddr3 Then
                            Arpreply() 'Call
                      End If
                   End If
                End If
              End If
            End If
         End If
      End If
      If Buffer(13) = &H00 Then                             'Type:IP
         If Buffer(14) = &H45 Then                          'We handle only simple IP packets
            If Buffer(20) = 0 Then                          'We handle only non fragmented packets
              If Buffer(30) = Ipaddr0 Then                  'Ip packet for us
                If Buffer(31) = Ipaddr1 Then
                   If Buffer(32) = Ipaddr2 Then
                      If Buffer(33) = Ipaddr3 Then
                        If Buffer(23) = 1 Then                       'Protocol:ICMP
                           If Buffer(34) = &H08 Then                 'ICMP echo request
                                Pingreply() 'Call
                           End If
                        End If
                        If Buffer(23) = 17 Then                      'Protocol:UDP
                        End If
                        If Buffer(23) = 6 Then                       'Protocol:TCP
                        End If
                      End If
                   End If
                End If
              End If
            End If
         End If
      End If

    End If

Lab Ende:

End Sub