Int 14 Fn 400A  - I1541 - Send A Byte To A Device                          [t]

   AX = 400Ah
   BL = byte to send
   CL = last-byte flag
       00h more bytes follow
       01h this is the last byte to be sent

Return: CF clear if successful
   CF set on error
       AL = error number (see #0280)

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