IADV - Advanced Mode and ICRN - CERN
Mode.Advanced &CERN Modes IADV sets the PCL in Advanced mode. MS4 through MS7 are recognised as
FASTBUS operations. This input should be wired either high (for
advanced mode) or low (for normal mode)
ICRN makes the PCL recognise the CERN MS4 Write operation as valid.
SS=0 is returned (rather than SS=6) but no other internal action is
performed. See Table 6. Section 11.5.
