;-*- Mode:Text -*-

Possible adjacent call hardware sequences:

Revised; no return-then-...

		(2nd)	no-op	open	call	o-c	return	t-open	t-call	cancel
(1st)		-------------------------------------------------------------------------
no-op		|	yes	yes	yes	yes	yes	yes	yes	yes	|
		|									|
open		|	yes	yes	yes	yes	-	-	-	(yes)	|
		|									|
call		|	yes	yes	-	yes	yes	yes	-	-	|
		|									|
open-call	|	yes	yes	-	yes	yes	yes	-	-	|
		|									|
return		|	yes	yes	yes	yes	***	yes	yes	(yes)	|
		|									|
t-open		|	yes	yes	-	yes	-	-	yes	(yes)	|
		|									|
t-call		|	yes	yes	-	yes	yes	yes	-	-	|
		|									|
cancel-open	|	yes	(yes)	(yes)	(yes)	-	(yes)	(yes)	(yes)	|
		-------------------------------------------------------------------------

(yes): supported, but not required.

***: supported, but not required if always using tail recursion.

Note that some combinations not shown are legal, but just not required.

;;;;;;;;;;;;;;;;

RETURN, RETURN works.

CANCEL-OPEN does not set up the next RPC and RD in time to be followed by RETURN.