Skip to content

Latest commit

 

History

History
54 lines (49 loc) · 995 Bytes

README.md

File metadata and controls

54 lines (49 loc) · 995 Bytes

PortA -- Input from host PortB:

  • 7- Input from host
  • 6- Output to host
  • 5- x
  • 4- x
  • 3- |
  • 2- | Output nibble ...
  • 1- | ... to host
  • 0- |

Init:

  • Set the directions
  • All outputs 0

WriteByteCoCo:

  • Write output upper nibble
  • Set OUT to high
  • Wait for IN from host is high
  • Set OUT to low
  • Wait for IN from host is low
  • Write output lower nibble
  • Set OUT to high
  • Wait for IN from host is high
  • Set OUT to low
  • Wait for IN from host is low

ReadByteCoCo:

  • Wait for IN from host is high
  • Read byte
  • Set OUT to high
  • Wait for IN from host is low
  • Set OUT to low
  • Return byte

WriteByteHost:

  • Write output byte
  • Set OUT to high
  • Wait for IN from host is high
  • Set OUT to low
  • Wait for IN from host is low

ReadByteHost:

  • Wait for IN from host is high
  • Read upper nibble
  • Set OUT to high
  • Wait for IN from host is low
  • Set OUT to low
  • Wait for IN from host is high
  • Read lower nibble
  • Set OUT to high
  • Wait for IN from host is low
  • Set OUT to low
  • Return byte