;  186 DIGITAL I/O FOR SCI M.R. HLU DI AND DO REPLACEMENT.
;
;  The SCI has 16 digital input words (read as 16 subaddresses of the 
;  186 card).  It also has 12 bits of digital output, which are used
;  for running the AC controllers.
;
;
;  READING AND BASIC STATUS PROPERTIES:
;
;	SSDN:	0000
;		0068  OID
;		ccnn  Crate and Slot
;		000a  A=subaddress (0-F)
;
;  [Wild card flag removed in port to VxWorks]
;  When the wild card flag is off, this device reads successive DI 
;  words from a single house.  The number of words is dictated by the 
;  'length' parameter in the 'DPREQ' call.
;
;  When the wild card flag is on, this device reads the same DI word
;  from all 24 non-zero houses.  The first address (crate and slot)
;  must be for house A1.  If the 'length' parameter is more than 24,
;  we proceed to read the next DI word all the way around the ring,
;  etc., so we can mimic slices out of the old MAC typecode 10 buffer.
;
;  The base DI channel number for wild card reads is in the SSDN.  We
;  do NOT automatically assume that you start from channel 0.
;
;  Actually, by using the 'length' and 'offset' parameters, it is
;  possible to get any slice out of this buffer.  Just remember that
;  the base DI channel in A1 is offset zero, and the house increments
;  faster than the DI channel number.
;
;  If we are doing a wild card read, and we get an error, we plug the
;  default error value into the data buffer.  We don't actually signal
;  an error.  In this way we can read past inoperative parts of the
;  ring.
;
;
;  BASIC CONTROL PROPERTY:
;
;	SSDN:	0000
;		0068  OID
;		ccnn  Crate and Slot
;		0000
;
;  The basic idea is to mimic the old MAC typecode 3.  Only the AC
;  controllers (old DO channel 8) are supported from the 186 card.
;  Be warned that the positions of the control bits have MOVED
;  within that control word.  Note also that the pulsing is now done
;  in hardware, you don't have to write the same bit three times
;  to make it go off-on-off.
;
;  You write 2 words for basic control:
;
;	Word 0:	House code (8-31), where A1=8 and F4=31
;	Word 1: Control mask: bit 'on' means pulse this bit.
;
;  Word 0 (the house code) is IGNORED for single-house (non-wild-card)
;  devices!
