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	TITLE	XPNPSI	- BLISSNET-10 PSI assist routines

; THIS SOFTWARE IS FURNISHED UNDER A LICENSE AND MAY  BE  USED
; OR COPIED ONLY IN ACCORDANCE WITH THE TERMS OF SUCH LICENSE.
;
; COPYRIGHT  (C)  DIGITAL  EQUIPMENT  CORPORATION 1985.
; ALL RIGHTS RESERVED.


	ENTRY	XPN$DPSI

	SEARCH	UUOSYM

	T1=1
	T2=2
	T3=3
	T4=4

	P=17

	BLKMAX=20		;Max routine addr storage

; This module contains the routines needed by BLISSNET-10 to use
; the PSI interface to TOPS-10.  It is necessary because it is impossible
; to save AC's at interrupt level in a BLISS routine.

; Start using the DIL standard edit history format.
; Facility: Blissnet
; Edit (%O'2', '12-Apr-84', 'Sandy Clemens')
;  %( Add the TOPS-10 BLISSnet sources for DIL V2.  )%
;
; Edit (%O'6', '5-Oct-84', 'Sandy Clemens')
;  %( Add new format of COPYRIGHT notice.  FILES:  ALL )%

; TOPS-10 PSI initialization
;
;	Notes: COBOL-10 V12B and FORTRAN-10 V7.0 do not use PSI
;
;	Hopefully, no users do either.  We must have it, but it is
;	very hard to share between non-cooperating routines.  In
;	7.01 they added a new PSI UUO (PISAV.) to get the PSI vector
;	address if it was already set up.  This is useful, but not
;	totally sufficient.  Which offset can we use?  We could look
;	for a free one (four words of zeros), but that may be
;	allocated to some other uninitialized routine.  We could put
;	ourselves into the interrupt chain on the first interrupt
;	block (each interrupt comes to us, we see it if is for us
;	(DECnet), if not, pass it to the previous owner of this
;	interrupt block).  But someone might overwrite that block,
;	then we stop getting interrupts!  So, until we can solve this
;	dilema, we will initialize the PSI system, and use it all
;	by ourselves!

; Module XPN$DPSI
;
; This module is called with the address of the routine the caller would
; like called on a DECnet interrupt.  This linkage is for BLISS, but could
; easily be done by MACRO as well.  This routine will initialize PSI and
; set up to received DECnet interrupts.  On each interrup the list of routines
; requesting notification will be called in turn with the PSI status word on
; the stack.  This routine will then do a WAKE UUO on this job in case we were
; hibernating, and dismiss the interrupt.
;
; If the caller specifies a zero address for its routine, we will not call it,
; but will issue the WAKE and dismiss the interrupt.

XPN$DPSI:
	DMOVEM	T1,T1T2			;Save AC's
	DMOVEM	T3,T3T4
	SKIPN	START			;Indicate that we have begun
	PUSHJ	P,PSIINI		;Need to start up PSI
	SKIPN	T2,-1(P)		;Routine
	  JRST	DPSI1			;Only wants a WAKE
	MOVE	T1,LSTLEN		;Get current LIST len
	CAIL	T1,BLKMAX		;LIST full?
	  JRST	TOOMNY			;That is bad
	ADDI	T1,1			;Next free word
	MOVEM	T2,LIST-1(T1)		;Save the routine address
	AOS	LSTLEN			;Remember new length
DPSI1:	DMOVE	T1,T1T2			;Restore AC's
	DMOVE	T3,T3T4
	POPJ	P,			;Return to caller

; INT
;
; Process interrupts.

; This routine is called whenever an interrupt is seen on

INT:	MOVEM	16,ACBLK+16		;Save AC16
	MOVEI	16,ACBLK		;BLT pointer
	BLT	16,ACBLK+15		;Save all but stack pointer
	SKIPN	LSTLEN			;Any routines to call?
	  JRST	INT2			;No, skip that part then
	MOVN	T1,LSTLEN		;Number or routines to call
	HRLZS	T1			;Make AOBJN pointer
	PUSH	P,T1			;Save this pointer over CALL
	PUSH	P,VECTOR+.PSVIS		;Save status word on stack
INT1:	MOVEM	T1,-1(P)		;Save current pointer
	PUSHJ	P,@LIST(T1)		;Call routine
	MOVE	T1,-1(P)		;Get back pointer
	AOBJN	T1,INT1			;Loop
	POP	P,(P)			;Clear the stack
	POP	P,(P)
INT2:	SETO	T1,			;Set to wake us
	WAKE	T1,			;Wake us
	  JFCL				;Not normally seen
	MOVE	16,[XWD ACBLK,0]	;Set up BLT pointer
	BLT	16,16			;Restore AC's
	DEBRK.				;Dismiss the interrupt




PSIINI:	SETOM	START			;We have been here now
	MOVE	T1,[XWD	1,T2]		;Get first word (flags)
	PISAV.	T1,			;Of PSI database
	  JFCL				;Block to short
	TLNE	T2,(PS.SON)		;Was it already in use?
	  JRST	PSIERR			;Yes, have to quit
	MOVEI	T1,VECTOR		;Address of vector
	PIINI.	T1,			;Initialize PSI
	  JRST	PSIERR			;Not good
	MOVE	T2,[EXP .PCNSP]		;Reason code DECnet
	SETZB	T3,T4			;Vector offset 0, prio=0, no I/O
	MOVE	T1,[EXP PS.FON!PS.FCP!PS.FAC!T2] ;Flags, address of args
	PISYS.	T1,
	  JRST	PSIERR			;Fatal
	POPJ	P,			;All initialized

PSIERR:	OUTSTR	[ASCIZ/
?XPNCIP Can not initialize the PSI interrupt system.
/]
	EXIT	1,
	JRST	.-1
TOOMNY:	OUTSTR	[ASCIZ/
?XPNTMY Too many calls to XPN$DPSI.
/]
	EXIT	1,
	JRST	.-1

ACBLK:	BLOCK	17			;Place to save AC's on INT
VECTOR:	EXP	INT			;Interrupt vector, new PC
	BLOCK	3
START:	EXP	0			;Init flag
LSTLEN:	EXP	0			;LIST length
LIST:	BLOCK	BLKMAX			;List of routines to call on INT
T1T2:	BLOCK	2			;Save T1, T2
T3T4:	BLOCK	2			;Save T3, T4
	END