In-System Debugging—IP2022 User’s Manual 346 www.ubicom.com 5.4 Host Connection to ISD/ISP Interface The ISD/ISP interface could be connected to an inexpensive and
already available interface, such as the parallel port of a PC driven
under software control, as shown in Figure 5-5. This would not
require any external hardware except a cable, but it will be slower
than an interface that implements data serialization in hardware. Figure 5-5  Simple ISD/ISP Interface Using  the  printer  or  USB  port  interface  to  communicate  with  a
Serial Debug Unit (SDU) with shift registers for data serialization,
as  shown  in  Figure  5-6,  provides  about  an  order  of  magnitude
performance  improvement  over  using  programmed  I/O  on  the
printer port.  Personal
Computer Printer Port   or
USB 515-050.eps Cable Target
System