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@ l0 : temp

@ l1 : constant 1

@ l2 : current address for memwrites

@ l3 : temp, holds the value received from uart

@ h1 : toggle bit = 0 zero, when a full 16 Bit word was received

@ h2 : holds the bitmask of the invalid instruction 0xffff = special with

@ l4 : temp, used for branch condition

80:

  ldi   l2, 0x80

  lsi   l2, 0x40     @ start of user program

  ldi   h2, 0xff

  lsi   h2, 0xff     @ h2 = 0xffff

  ldi   l1, 1        @ constant 1

  ldi   h1, 0        @ toggle bit (hi low)

  stio  h2, [h1]     @ leds echo

1: @ wait for byte

  ldi   l0, 0x80     @ uart status address

  ldio  l3, [l0]

  ldi   h0, 2        @ uart data ready bit

  and   l4, l3, h0

  brz   l4, :1

  ldi   h0, 0x81     @ uart data address

  ldio  l3, [h0]     @ uart rcv

  xor   h1, h1, l1   @ toggle state (16 bit Ready)

  stio  l3, [h0]     @ uart echo (uart should be ready at this point)

  ldi   h0, 0x00         @ leds address

  stio  l3, [h0]     @ leds echo

  brz   h1, :2

  nop                @ hier könnte leds echo sein (nop wegen evtl.  Simulator bug)

  @ olny first half (LSB) of instruction was received

  brnz  h1, :1

  mov   h3, l3       @ h3: holds 16-bit instr (here LSB are set)

2: @ full 16-Bit instruction is ready

  shi   l3, 8        @ move received 8 bits

  or    h3, h3, l3   @ merge the two instructionbytes

  stio  h3, [l2]     @ write instruction to programm-mem

  xor   l4, h3, h2   @ check if the instruction writen to pmem is 0xffff

  brnz  l4, :1

  adi   l2, 1        @ increase program-write address

@@ programm loaded

@ jump to begin of loaded program

  ldi   l0, 0x40

  jump  

  nop