Int 14 Fn 400B  - I1541 - Receive A Byte From A Device                     [t]

   AX = 400Bh

Return: CF clear if successful
       AL = byte received
       CL = last-byte flag
       00h more bytes to follow
       01h received byte is the last
   CF set on error
       AL = error number
       80h EOI response required
       81h talker not ready
       82h clock not set
       83h clock not released
       CL = 00h

See Also: AX=4000h,AX=400Ah