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Trailing-Edge - PDP-10 Archives - bb-m780a-sm - monitor-sources/impanx.mac
There are 16 other files named impanx.mac in the archive. Click here to see a list.
; UPD ID= 543, SNARK:<5.MONITOR>IMPANX.MAC.10,  16-Mar-82 20:11:51 by PAETZOLD
;TCO 5.1755 - Send three NOPs in IMIERR
; UPD ID= 109, SNARK:<5.MONITOR>IMPANX.MAC.9,  20-Aug-81 15:19:56 by ZIMA
;TCO 5.1458 - Change title for Autopatch consistency.
; UPD ID= 77, SNARK:<5.MONITOR>IMPANX.MAC.8,  27-Jul-81 09:06:11 by PAETZOLD
;UPDATE COPYRIGHT INFORMATION
; UPD ID= 72, SNARK:<5.MONITOR>IMPANX.MAC.7,  24-Jul-81 05:21:13 by PAETZOLD
; UPD ID= 70, SNARK:<5.MONITOR>IMPANX.MAC.6,  23-Jul-81 16:03:10 by PAETZOLD
;TCO 5.1380 - Add IMPFPF routine to determine if AN10 caused IOPGF
; UPD ID= 2032, SNARK:<5.MONITOR>IMPANX.MAC.5,  19-May-81 13:15:02 by PAETZOLD
;FIX TYPO IN LAST EDIT IN IMIERR
; UPD ID= 1991, SNARK:<5.MONITOR>IMPANX.MAC.4,  14-May-81 11:23:27 by PAETZOLD
;TCO 5.1321 MAKE ARPANET WORK IN RELEASE 5
;CHANGE ORDER OF FILE NAMES IN SEARCH PSEUDO OP
;DONT CYCLE NET IN IMIERR IF DEBUGGING
; UPD ID= 720, SNARK:<5.MONITOR>IMPANX.MAC.3,   1-Jul-80 15:21:22 by LYONS
; UPD ID= 719, SNARK:<5.MONITOR>IMPANX.MAC.2,   1-Jul-80 15:12:37 by LYONS
; TCO 5.1088 IMPNII, ILLUUO do to trashed stack in IMIN3
;   also, if IMIERR is called, punt the network, and reset all connections
;<4.1.MONITOR>IMPANX.MAC.19,  3-Jan-80 08:39:19, EDIT BY R.ACE
;CHANGE BBN TO DEC IN COPYRIGHT NOTICE
;<4.MONITOR>IMPANX.MAC.18, 11-Oct-79 14:40:29, Edit by LCAMPBELL
; Document BUGHLTs
;<OSMAN.MON>IMPANX.MAC.1, 10-Sep-79 15:33:19, EDIT BY OSMAN
;TCO 4.2412 - Move definition of BUGHLTs, BUGCHKs, and BUGINFs to BUGS.MAC
;<4.MONITOR>IMPANX.MAC.16, 20-Apr-79 14:58:31, Edit by LCAMPBELL
; Merge in BBN changes
;<4.MONITOR>IMPANX.MAC.15, 18-Apr-79 12:40:40, Edit by LCAMPBELL
; Clear IMPOB also after sending irregular messages
;<4.MONITOR>IMPANX.MAC.14, 13-Apr-79 15:14:40, Edit by LCAMPBELL
; When done with an output buffer, clear IMPOB to prevent IMPAFB
;<4.MONITOR>IMPANX.MAC.13, 26-Jan-79 09:48:22, Edit by LCAMPBELL
;<4.MONITOR>IMPANX.MAC.12,  9-Jan-79 13:53:33, Edit by LCAMPBELL
; Update copyright notice
;<4.MONITOR>IMPANX.MAC.11,  5-Jan-79 11:12:55, Edit by LCAMPBELL
; Change IMPRST to IMPINI, it's more mnemonic
;<4.MONITOR>IMPANX.MAC.10,  3-Jan-79 13:02:55, Edit by LCAMPBELL
; Add definition of STY%NP removed from IMPPAR
;<4.MONITOR>IMPANX.MAC.8, 29-Sep-78 13:58:13, Edit by LCAMPBELL
; Add dummy entry point IMPRST (is non-dummy for IMP11B)
;<4.MONITOR>IMPANX.MAC.2,  3-Sep-78 23:26:29, EDIT BY JBORCHEK
;<3A-JBORCHEK>IMPANX.MAC.3, 24-Aug-78 20:17:44, EDIT BY JBORCHEK
;<4.MONITOR>IMPANX.MAC.4, 22-Aug-78 14:15:32, EDIT BY JBORCHEK
;CONDITIONALIZE BBN CODE
;<BBN-3-MONITOR>IMPANX.MAC.1,  4-Aug-78 14:54:48, EDIT BY CLEMENTS
; Against my better judgment, introduce conditional on TCP assembly.
;<3-CLEMENTS>IMPANX.MAC.8, 15-Jun-78 14:25:51, EDIT BY CLEMENTS
; Note: Internet stuff has been disabled at INETIN until TCP and
; its buffers get converted to rel 3.
;<3-CLEMENTS>IMPANX.MAC.2,  8-Jun-78 17:21:55, EDIT BY CLEMENTS
;<3-CLEMENTS>IMPANX.MAC.1,  8-Jun-78 17:07:00, EDIT BY CLEMENTS
; Start converting for release 3, extended addressing. Including
; long leaders, and DEC additions.
;COPYRIGHT (C) 1978,1979,1980,1981 BY DIGITAL EQUIPMENT CORPORATION, MAYNARD, MASS.

TCPF==0	;*** TEMPORARILY, INTRODUCE AN ASS'Y SWITCH, TURNING OFF TCP
BBNF==0	;*** BBN ONLY CODE ***

SEARCH IMPPAR,PROLOG
SEARCH MACSYM,MONSYM

	TTITLE (IMPANX,IMPANX,< -  IMP DRIVER FOR AN10 - R CLEMENTS>)


; HARDWARE DEFINITIONS FOR AN10 DEVICE INTERFACE

ANI=520		;I/O DEVICE NUMBER FOR INPUT SIDE
ANO=524		;I/O DEVICE NUMBER FOR OUTPUT SIDE

;BITS IN CONI FOR ANI

ANIMRQ==1B27	;MSG REQUEST. IMP STARTING TO SEND TO HOST.
ANIBSY==1B26	;BUSY. HOST IS ACCEPTING A MESSAGE
ANIM36==1B25	;MESSAGE BEING ASSEMBLED INTO 36 BIT WDS IF 1,
		; 32 BIT WORDS IF 0.
ANIWCO==1B24	;WD COUNT OVERFLOW. MESSAGE PORTION IS DONE.
ANIDON==1B23	;DONE. IMP SENT LAST BIT.
ANIIID==1B19	;IMP IS DOWN. (READY LINE OFF)
ANIIWD==1B18	;IMP WAS DOWN. (READY LINE HAS BEEN OFF)

;BITS IN CONO FOR ANI

ANIRST==1B19	;RESET THE WHOLE AN10 (EXCEPT HOST READY LINE)
ANICLE==1B18	;CLEAR ERROR FLAGS IN LH OF CONI, CLR IMP WAS DOWN.
ANXCHS==6B32+6B35;TWO ADJACENT PI CHANNELS IN B30-35
;BITS IN CONI FOR ANO

ANOEND==1B27	;END OF MSG. SEND "LAST" WHEN WD CNT RUNS OUT.
ANOBSY==1B26	;BUSY. SEND WORDS TO THE IMP.
ANOM36==1B25	;MODE 36. SEND ALL 36 BITS OF DATA WORDS. ELSE,
		; JUST SEND LEFT-HAND 32 BITS.
ANOWCO==1B24	;WORD COUNT OVERFLOW. THIS MSG PORTION COMPLETED.
ANODON==1B23	;ALL BITS INCLUDING "LAST" HAVE BEEN SENT.
ANOIID==1B19	;IMP IS DOWN, SAME AS IN ANI
ANOIWD==1B18	;IMP WAS DOWN, SAME AS IN ANI

;BITS IN CONO FOR ANO

ANOCLE==1B18	;CLEAR ERROR BITS, IMP WAS DOWN BIT.

;REGISTER SELECT FIELD, IN BOTH ANO AND ANI CONO'S
; NOTE THESE AREN'T USED MUCH BECAUSE HARDWARE SWITCHES TO
; THE "RIGHT" REGISTER MOST OF THE TIME BY ITSELF.

ANXVAR==2B29	;VECTOR INTERRUPT ADDRESS REGISTER
ANXWAR==1B29	;WORD COUNT AND ADDRESS REGISTER
ANXDR==0B29	;DATA REGISTER.

; BITS IN INPUT DEVICE VECTOR ADDRESS REGISTER

ANIHRL==1B10	;HOST READY LINE. DATAO A 1 TO BECOME READY.

;MISCELLANEOUS VARIABLES

PIMSTK::IOWD NIMSTK,IMSTK	;IMP INTERRUPT STACK POINTER

DEFSTR IMWDCT,,12,12		;WORD COUNT FOR WC/ADR REGISTER
DEFSTR IMBFAD,,35,23		;ADDRESS FOR WC/ADR REGISTER

;INTERRUPT LOCATION

ANOVIL:	XPCW ANOVI1		;OUTPUT INTERRUPT LOCATION

ANIVIL:	XPCW ANIVI1		;INPUT INTERRUPT LOCATION

;Device-dependent data for leaders

	STY%NP==5		;Number of Padding words, for H2I NOP
;CLOCK LEVEL CHECK ROUTINE

IMPCHK::MOVEI T2,^D1000
	MOVEM T2,IMPTM2		; Call this every second
	SKIPN IMPRDY		; Net on?
	 JRST IMPCKX		; NO.
	CALL IMPRLQ		; IS IMP DOWN NOW OR RECENTLY?
	 SKIPL IMPRDT		; And not already noticed?
	JRST IMPCKX		; NO. NO NEED TO SET ERROR FLAGS
	CALL IMIERR		; Be sure it's noticed
	AOS IMPFLG		; cause running of ncp fork
IMPCKX:
IFN BBNF,<
	CALL IM2CHK		; Check second interface, if any
>
	RET
; Start input
; called from process level when buffers made available and input is off
; and from endin processor if more buffers are available

IMISRT::CALL IMPRLQ		; IS DEVICE UP AND IMP READY?
	 RET			; No, do nothing
	SOSL IMPNFI
	SKIPN T1,IMPFRI
	 BUG(IMPNII)
	LOAD T2,NBQUE,(T1)	; Get next free buffer
	SKIPE T2		; If there's a successor,
	HRLI T2,ANBSEC		; Set section number
	MOVEM T2,IMPFRI
	SETZRO NBQUE,(T1)	; DeQueue it from any others
	MOVEM T1,IMIB
   IFN TCPF,<
	HRRZS TNBFFL		; Remember IMIB is an NCP buffer
   >
	HRRI T1,.NBLD0(T1)	; FIRST WORD TO READ INTO
	TLO T1,(<.NBLD2+1>B12)	; Read thru leader and some padding
	MOVEM T1,IMPINP		; THIS IS THE FIRST DATAO TO ANXWAR
	MOVE T1,[MSEC1,,IMIN0]	; SET STATE TO "WAITING FOR IMP TO GO"
	MOVEM T1,IMIDSP
	SETZM IMPIOV		; AND CLEAR "INPUT OVERFLOW" FLAG
	CONSZ ANI,ANIIWD	; HAS IMP BEEN DOWN?
	 CALL IMIERR		; YES, Be sure it gets noticed
	CONO ANI,ANICLE+ANXWAR+ANXCHS	;TELL IMP WE ARE READY TO GO.
	RET			; IT WILL INTERRUPT ON FIRST BIT TO US
; Pi service for input
; No AC's have been saved!
; Dispatched via IMIDSP to various routines.
; IF ANIDON IS ON, THEY GO TO IMPEIN FOR END OF INPUT HANDLING.

;For subsequent interrupts, a field will steer the packing and counts.
;Values are named .IIxxx for Imp Interrupt dispatch. Store in IMITYP
; for input and similarly in IMOTYP for output.

.IINC6==0		;This is a 36 bit NCP message
.IINC2==1		;This is a 32 bit NCP message
.IITNT==2		;Telenet link
.IISPQ==3		;Special queue
.IIINT==4		;Internet packing
.IIMLC==5		;MLC (Ptip) format
.IISQ2==6		;False start on Internet -- Handle as spec. Q.

; Here when input has been idle and IMP starts to send bits.
; This first interrupt requires us to send over word count and
; address. The first count will read the IMP-to-host leader and
; a word of padding, in 36 bit mode.

IMIN0:	CONSO ANI,ANIMRQ	;MESSAGE REQUEST IS ONLY VALID BIT
	JRST IMIN0X		;IT WASN'T THAT. SOMETHING WIERD.
	MOVEM T1,IMIDSP		;SAVE AC T1, PREPARE TO SET DISPATCH.
	MOVE T1,[MSEC1,,IMIN1]	;NEXT INTERRUPT WANTED IS THIS
	EXCH T1,IMIDSP		;SET DISPATCH FOR READING I-H LEADER.
	DATAO ANI,IMPINP	;TELL IT BUFFER ADDRESS AND COUNT.
	CONO ANI,ANIM36+ANIBSY+ANXCHS	;SET TO READ 36 BITS, THEN PI.
	XJEN ANIVI1		;DISMISS INPUT INTERRUPT.

;IMIN0X - Input interrupt error routine. If the input side of the
; ANX has been idle, any interrupt other than MSG REQUEST is an error.

IMIN0X:	MOVEM T1,IMIDSP		;SAVE T1
	CONI ANI,T1		;GET STATUS, FOR BUGINF TO SEE
	CONO ANI,0		;TURN OFF INPUT.
	BUG (IMINX1,<<T1,CONIAN>>)
	MOVE T1,[MSEC1,,IMIN0X]	;SET DISPATCH ADDRESS
	EXCH T1,IMIDSP		;AND RESTORE T1
	CONO ANI,ANIRST		;RESET ANI, LEAVE ANIIWD ON, IMPUT OFF
	XJEN ANIVI1		;AND LET CLOCK/NCPFRK FIX IT.
; Here at PI level after IMP leader and a word of padding
; have been read. ANIDON on means it wasn't that long.
; If not end of message, decide whether to read some more
; in 32 or 36 bit mode, based on link and host numbers so far.
; For NCP, will still have to read H-H leader and then decide again.

IMIN1:	CONSZ ANI,ANIDON	;END OF MESSAGE YET?
	JRST IMPEIN		;Yes, go process short (irreg) msg
	DMOVEM T1,IMPIAC+T1	;Save standard interrupt level AC's
	DMOVEM T3,IMPIAC+T3	; ..
	DMOVEM CX,IMPICX	; ..
	MOVE P,PIMSTK		; And set up a local PI level stack
	MOVE T1,IMIB		;Point to the input buffer
	LOAD T2,IHLNK,(T1)	;Get the link and host numbers
	LOAD T3,IHHST,(T1)	; ..
IFN BBNF,<
	MOVEI T4,0(T2)		;Shift for MLC field
	LSH T4,-1		; ..
	CAMN T4,MLCHLF		;Right link for MLC?
	JRST IMI1ML		;Yes
	CAIN T2,TNTLNK		;Is it the TELENET link?
	JRST IMI1TN		;Yes, pack it differently
	CAIN T2,INTLNK		;Internet Link?
	JRST IMI1IN		;Yes.  Mark that in IMIDSP.
>
	CAIG T2,LLINK		;Check for NCP or not
	CAIL T3,FKHOST		; ..
	JRST IMI1SQ		;Not NCP. Treat special queues.
IMI1NC:	MOVX T4,.IINC6		;Will want NCP handling
IMIN1A:	MOVEI T2,.NBLD2+2(T1)	;Where next word in goes.
	HLL T2,II1WCT(T4)	;Word count
	TLO T2,ANBSEC		;In right addr space
	MOVEM T2,IMPINP		;Command for device
	DATAO ANI,IMPINP	;Load WC and address
	CONO ANI,@II1CNO(T4)	;Make it go
	MOVE T3,[MSEC1,,IMIN2]	;Address for next interrupt
	MOVEM T3,IMIDSP		;Save for next interrupt
	MOVEM T4,IMITYP		;Save dispatch code
	JRST IMPUB1		;Done with this int'pt.
IMI1SQ:	MOVX T4,.IISPQ		;Special queues
	JRST IMIN1A		;Join common code

IFN BBNF,<
IMI1ML:	MOVX T4,.IIMLC		;MLC link
	JRST IMIN1A		;Join common code

IMI1IN:	MOVX T4,.IIINT		;Internet code
	JRST IMIN1A		;Join common code

IMI1TN:	MOVX T4,.IITNT		;Telenet handling code
	JRST IMIN1A		;And join NCP flavor routine
>

II1WCT:	EXP 2B12		;TYPE NCP36
	EXP 2B12		;TYPE NCP32
	EXP 2B12		;TYPE TELENET
	EXP 1B12		;TYPE SPECIAL Q
	EXP 4B12		;TYPE Internet
	EXP 2B12		;TYPE MLC
	EXP 2B12		;should not be referenced here

II1CNO:	EXP ANIM36+ANIBSY+ANXCHS	;TYPE NCP36
	EXP ANIM36+ANIBSY+ANXCHS	;TYPE NCP32
	EXP ANIM36+ANIBSY+ANXCHS	;TYPE TELENET
	EXP ANIBSY+ANXCHS		;TYPE SPECIAL Q
	EXP ANIBSY+ANXCHS		;TYPE Internet
	EXP ANIM36+ANIBSY+ANXCHS	;TYPE MLC
	EXP ANIM36+ANIBSY+ANXCHS	;should not be referenced here
IMIN2:	CONSZ ANI,ANIDON	;End of message yet?
	JRST IMPEIN		;Yes. Go process short message
	DMOVEM T1,IMPIAC+T1	;Save standard interrupt level AC's
	DMOVEM T3,IMPIAC+T3	; (Since here by vectored interrupt)
	DMOVEM CX,IMPICX	; ..
	MOVE P,PIMSTK		; And set up a local PI level stack
	MOVE T1,IMIB		;Point to the input buffer
	MOVE T4,IMITYP		;Get type code for this message
;Padding removal isn't needed if haven't read that much, but it's
; cheaper to always remove it than to test for needing to.
	MOVE T2,.NBLD2+2(T1)	;Crunch out the padding on input
	STOR T2,IHPD1,(T1)	;Move this partial word
	MOVE T2,.NBHHL+2(T1)	;And this full one
	MOVEM T2,.NBHHL(T1)	; ..
IFN BBNF,<
	CAIN T4,.IIINT		;Inputting possible Internet msg?
	 CALL INETIN		;Check further. May change T4,T1.
>
	LOAD T2,NBBSZ,(T1)	;Get its size
	MOVE T3,II2LDT(T4)	;Amount we have used so far
	SUBI T2,(T3)		; ..
	ASH T2,^D23		;Position for AN10 word counter
	HRR T2,T1		;Address of the buffer
	ADDI T2,(T3)		;Word in buffer that we want to write
	TLO T2,ANBSEC		;In the right section
	MOVEM T2,IMPINP		;Feed this to the hardware
	DATAO ANI,IMPINP	;Tell it.
	CAIE T4,.IINC6		;NCP links?
	JRST IMIN2A		;No.
	LOAD T2,HHSIZ,(T1)	;Yes, see if 32 bit or 36.
	CAIN T2,^D36		;Check connection byte size
	JRST IMIN2A		;36 bit connection
	MOVEI T4,.IINC2		;Change type to 32 bit NCP
	MOVEM T4,IMITYP		;Remember dispatch type in core
IMIN2A:	CONO ANI,@II2CNO(T4)	;Make it go
	MOVE T1,[MSEC1,,IMIN3]	;SET DISPATCH FOR NEXT INTERRUPT
	MOVEM T1,IMIDSP		; ..
	JRST IMPUB1		;Restore AC's and dismiss interrupt

;Table of CONO values to read data portion of message, by msg type

II2CNO:	EXP ANIM36+ANIBSY+ANXCHS	;TYPE NCP36
	EXP ANIBSY+ANXCHS		;TYPE NCP32
	EXP ANIM36+ANIBSY+ANXCHS	;TYPE TELENET
	EXP ANIBSY+ANXCHS		;TYPE SPECIAL Q
	EXP ANIBSY+ANXCHS		;TYPE Internet
	EXP ANIM36+ANIBSY+ANXCHS	;TYPE MLC
	EXP ANIBSY+ANXCHS		;TYPE SPECIAL Q - false internet

;Table of next word to read into at IMIN2 time, by message type

II2LDT:	EXP .NBDW0		;Type NCP36
	EXP .NBDW0		;Type NCP32
	EXP .NBDW0		;Type TELENET
	EXP .NBHHL		;Type SPECIAL QUEUES
	EXP .NBDW0+2		;Type Internet
	EXP .NBDW0		;Type MLC
	EXP .NBHHL+3		;Type Special Q - false Internet
;NOTE: This code is disabled for the time being.

; Called from IMIN2 when possible Internet message is coming in.
; This routine does the following:
;	1.	Move the 2 remaining H-H words to the right place
;	2.	Check for right message type and subtype
;	3.	Check for right Internet message type
;		(Currently just TCP format is handled)
;	4.	Check for TCP being on -- TCP fork runs the gateway
;	5.	Check for a TCP-supplied buffer being available
; If any of those conditions is lacking, input is resumed and the
; message is handled as a normal special queue message.
; If the message is really destined for the gateway (TCP, XNET, ...),
; it gets copied into a TCP-supplied buffer and input resumes.
; IMPEIN will then queue it for the gateway.

;T1/	Pointer to current NCP-supplied buffer
;	CALL INETIN
;Ret+1:	Always. T4 set to .IIINT if I.N. msg to be completed, or .IISQ2
;		if it will be given to a special Q


IFN BBNF,<
INETIN:	DMOVE T2,.NBDW0+2(T1)	; Pick up the Internet header
	DMOVEM T2,.NBDW0(T1)	; Stash in proper place
   IFN TCPF,<			;Until TCP done for rel 3
	LOAD T2,IHFTY,(T1)	; ARPANET message format
	LOAD T3,IHMTY,(T1)	; ARPANET message type
	CAIN T3,.IHREG		; Regular msg?
	CAIE T2,ITY%LL		; Long leader?
   > ; End TCP code
	 JRST INETIC		; No. Let normal code handle it.
   IFN TCPF,<			;Until TCP done for rel 3
	LOAD T2,IHSTY,(T1)	; ARPANET subtype
	CAIE T2,STY%FC		; Normal, flow-controlled?
	CAIN T2,STY%UC		; or uncontrolled?
	SKIPN TCPON		; And TCP is on? (It runs the gateway)
	 JRST INETIC		; No.  Let normal code handle this.
	LOAD T2,INETF,(T1)	; Get Internet Format and Version
	CAIN T2,<.TCPFM_4>+.TCPVR ; OK for TCP (**** Current Limitation)
	SKIPG TCPNFI		; And there is a TCP buffer around?
	 JRST INETIC		; No.  Let normal special queue have it.

; All is OK for the switch to a TCP buffer.  Do it, return the NCP buf.

	SOSL TCPNFI		; Count down number of free TCP bufs
	SKIPN T2,TCPFRI		; Get pointer to buffer to use
	 BUG(IMPNIT)
	HRLI T3,.NBLD0(T1)	; "From" pointer for BLT
	HRRI T3,.NBLD0(T2)	; "To" -- into TCP buffer
	HLRZ T4,II1WCT+.IIINT	; Get size of second transfer
	ADDI T4,.NBHHL-2(T2)	; Compute last addr (-2 for fill crunch)
;;; Figure out where these buffers will live, and call XBLTA here.
	BLT T3,0(T4)		; Copy ARPANET and Internet headers
	HLRZ T1,0(T2)		; Next TCP free buffer
	EXCH T1,TCPFRI		; Becomes head of list
	EXCH T1,IMIB		; Old head is now current input bfr
	EXCH T1,IMPFRI		; Old input bfr goes to NCP free list
	HRLM T1,@IMPFRI		; Old list is off of new head
	AOS IMPNFI		; There is now another free input bfr
	HRROS TNBFFL		; The current one is owned by TCP
	MOVEI T1,0(T2)		; Now think in terms of TCP's buffer
	MOVEI T4,.IIINT		; Return this to caller
	RET
   > ; End TCP code

; Here when current input is to be continued.  Fix to be spec. q. input.

INETIC:	MOVEI T2,.IISPQ		; Mark for special Queue dispatch
	MOVEM T2,IMITYP		; On next interrupt
	MOVEI T4,.IISQ2		; Return this to caller
	RET
>

;HERE ON INTERRUPT LEVEL FOR BODY OF MESSAGE FROM IMP.

IMIN3:	CONSZ ANI,ANIDON	;I HOPE IT FIT IN THE BUFFER.
	JRST IMPEIN		;GOOD. IT DID.
	AOS IMPIOV		;IT DIDN'T. FLAG THAT IT'S TOO LONG.
	DATAO ANI,[1B12+IMSTK+NIMSTK-1] ;Use stack as bit bucket
	CONO ANI,ANIBSY+ANXCHS	;KEEP READING UNTIL END COMES ALONG.
	XJEN ANIVI1		;WAIT FOR NEXT INTERRUPT. END, PLEASE?
; Here when end msg recd from imp

IMPEIN:	DMOVEM T1,IMPIAC+T1	;Save standard interrupt level AC's
	DMOVEM T3,IMPIAC+T3	; ..
	DMOVEM CX,IMPICX	; ..
	MOVE P,PIMSTK		; And set up a local PI level stack
	CONSZ ANI,ANIIWD!ANIIID	; IMP IS OR WAS DOWN?
	 CALL IMIERR		; Take care of it
	CONO ANI,ANXWAR		; SELECT WC/ADDR REGISTER, CLEAR PIA
	DATAI ANI,IMPINP	; READ CURRENT ADDRESS
	SKIPG T1,IMIB		; Bfr address
	JRST IMPEI2		; Wasn't one
	AOSLE IMPFLS		; Flushing msgs?
	SKIPE IMPIOV		; OR GOT AN OVERFLOW?
	 JRST IMPEI3		; Yes, return to free list
	HRRZ T2,IMPINP		; How much was read?
	CAIGE T2,.NBLD2(T1)	; A full leader?
	JRST IMPEI3		; No, Discard it as useless
	LOAD T3,IHFTY,(T1)	; Is this a long leader msg?
	CAIE T3,ITY%LL		; ..
	JRST IMPEI3		; No. Just throw it away.
	LOAD T3,IHMTY,(T1)	; Yes. Get message type.
	CAIE T3,.IHIGD		; One of the ones that has no msg ID?
	CAIN T3,.IHDHS		; ..
	JRST IMPEI4		; Yes. Give it to NCP
	CAIN T3,.IHNOP		; You also can't believe link on NOPs
	JRST IMPEI4		; Give them to NCP anyhow
	LOAD T2,IHHST,(T1)	; See whether it's an NCP irreg msg
	LOAD T4,IHLNK,(T1)	; Get host and link
	CAIGE T2,FKHOST		; From IMP fake hosts?
	CAILE T4,LLINK		; Or non-NCP Link?
	CAIA			; Yes, not for NCP
	JUMPN T3,IMPEI4		; Give irreg msg to NCP
;Falls thru to IMPEI0
;Falls thru

IMPEI0:
   IFN TCPF,<
	SKIPGE TNBFFL		; Skip if TCP does not own IMIB
	 JRST [	HRLM T1,@TCPIBI	; Queue for Gateway
		HRRZM T1,TCPIBI
		AOS TCPFLG	; Cause TCP process to notice it
		JRST IMPEI1]	; Avoid running NCP -- TCP buffer used
   >
IFN BBNF,<
	CAIN T4,TNTLNK		; TELENET LINK
	 JRST TNTEIN		; YES-PROCESS
	LSH T4,-1		; Link field for MLC traffic?
	CAMN T4,MLCHLF		; Is it the MLC link field?
	 JRST IMPEIP		; YES-DO PTIP STUFF
>
	MOVE T3,IMPIBI		; Add to NCP fork's queue
	JUMPN T3,IMPEIA		; Anything on it already?
	MOVEM T1,IMPIBO		; No. This is it, then.
	SKIPA			; Don't chain it
IMPEIA:	HRLM T1,0(T3)		; Add buffer to input queue for NCPFRK
	MOVEM T1,IMPIBI		; This is the last guy on queue
	AOS IMPFLG		; Request job 0 service
IMPEI1:	LOAD T3,NBBSZ,(T1)	; Make sure not a released buffer
	CAMLE T3,MAXWPM		; by checking size field for a PC
	 BUG (IMPAUF)
   REPEAT 0,<			;DEC DECIDED TO LOCK BUFFERS ONLY ONCE
	PUSH P,T1		; Save buffer address
	ADD T1,T3		; Compute tail of bfr
	MOVEI T1,-1(T1)
	CALL MULKMP		; Unlock it
	POP P,T1		; Restore base of buffer
   > ; End of repeat 0
	LOAD T3,IMBFAD,IMPINP	; GET LAST LOC WITH DATA +1
	SUB T3,IMIB		; Less base of the buffer
	STOR T3,NBBSZ,(T1)	; RECORD ACTUAL COUNT IN BUFFER HEADER
IMPEI2:	SETZM IMIB
	SKIPLE IMPNFI		; More buffers available?
	 CALL IMISRT		; Yes, start new input
IMPUB1:	DMOVE T1,IMPIAC+T1	; Restore AC's from before PI
	DMOVE T3,IMPIAC+T3
	DMOVE CX,IMPICX
	XJEN ANIVI1		; AND DISMISS INPUT INTERRUPT
IFN BBNF,<

IMPEIP:	MOVE T3,MLCIBI		;ANYTHING ON PTIP INPUT QUEUE YET?
	JUMPN T3,IMPEP2		;JUMP IF SO
	MOVEM T1,MLCIBO		;NO, SO THIS IS THE FIRST ONE OUT
	SKIPA			;DON'T TRY TO LINK IT
IMPEP2:	HRLM T1,0(T3)		;LINK TO PREVIOUS LAST-IN
	MOVEM T1,MLCIBI		;THIS IS NEW LAST-IN
	MOVE T3,IMPNIB		; GET INPUT BUFFER THRESHOLD
	LSH T3,-1		; HALVE
	CAML T3,IMPNFI		; DO WE HAVE MORE THAN THAT ON TAP?
	AOS IMPFLG		; NO, GOOSE THE NCP SO IT WILL NOTICE
	JRST IMPEI1		; THAT MLC STOLE AN INPUT BUFFER


;GET A TELENET BUFFER AND XFER FROM ARPANET BUFFER TO IT

TNTEIN:	PUSH P,P1		;TNET'S MESSAGE POINTER
	MOVE P1,T1		;GET ANBSEC,,ADR OR ARPA BUFF
	SUBI P1,1		;TAKE CARE OF OFFSET
	CALL GETMBF		;LET IT BLESS TEXT, GET A BUFFER.
	JUMPL P1,TNTEIX		;JUMP IF NO BUFFER AVAIL
	MOVE T2,IMIB		;FROM HERE
	MOVE T3,P1		;TO HERE
	ADDI T3,1		;WITH OFFSET
	HRRZ T1,IMPINP		;ADR OF NEXT WORD TO BE FILLED
	HRRZ T4,IMIB		;GET ADR OF START OF BUFFER
	SUBI T1,-1(T4)		;T1/ # WORDS READ
	HRRZ T4,1(P1)		;GET TELENET BUFFER'S LENGTH
	CAMGE T4,T1		;BIG ENOUGH FOR FULL BLT?
	 JRST TNTEIX		;NO - LOSE BUFFER
	AOS T2			;DON'T GET OVERHEAD WORD
	AOS T3			;DON'T CLOBBER SIZE WORD IN TEL BUFF
	SOS T1			;THEREFORE 1 LESS WORD TO DO
	CALL XBLTA		;YES-DO XFER OF DATA
	CALL TNTRCV		;P1/ ADR OF TNT BUFF JUST FILLED
TNTEIX:	MOVE T1,IMIB		;RECOVER POINTER TO ARPANET BUFFER
	POP P,P1		;RESTORE AC
	JRST IMPEI6		;NOW FREE ARPA BUF SINCE WAS COPIED

> ;END IFN BBNF
IMPEI4:	CALL IMP8XQ		; Put on irreg msg Q for NCP
	AOS IMPFLG		; Awaken NCP
IMPEI3:
   IFN TCPF,<			; Until TCP done
	SKIPL TNBFFL		; IMIB owned by NCP?
	 JRST IMPEI6		; Yes.  Release to normal area
	EXCH T1,TCPFRI		; Release to TCP
	HRLM T1,@TCPFRI
	AOS TCPNFI		; Count another free buffer
	JRST IMPEI2
   >
IMPEI6:	MOVE T2,T1		; Current buffer address
	EXCH T1,IMPFRI		; Return buffer to Free Input list
	HRLM T1,0(T2)		; Make it point to old top of list
	AOS IMPNFI		; Count another free buffer
	JRST IMPEI2

IMIERR:	PUSH P,T1
	SETOM IMPRDL		; Be sure this flap gets noticed
	MOVNI T1,2
	MOVEM T1,IMPFLS
	MOVEI T1,3		; GET NUMBER OF NOPs to send
	MOVEM T1,NOPCNT		; Send some nops
	CONI ANI,T1		; SEE IF PIA'S ARE NOW ON
	BUG (IMINX2,<<T1,CONIAN>>)
	ANDI T1,77
	CONO ANI,ANICLE(T1)	; CLEAR THE ERROR FLOP
	MOVE T1,DBUGSW		; GET THE STATE OF DEBUGGING
	CAIE T1,2		; ARE WE DEBUGGING?
	 AOS IMPDRQ		; NO SO Cycle the net
	JRST PA1		; RESTORE AC T1, RETURN.
; Routine to start msg going out. called at pi level, and at
; Main level if no output in progress

IMPXOU::PIOFF
	SKIPN IMPOB		; ANY OUTPUT IN PROGRESS?
	 JRST IMPXO1		; NO
	PION			; YES, TURN PI BACK ON
	JRST (T4)		; AND RETURN

IMPXO1:	SETOM IMPOB		; MARK OUTPUT IN PROGRESS
	PION			; NO IT'S OK TO TURN PI BACK ON
	PUSH P,T4		; SAVE RETURN
IMPIOU:	SKIPLE NOPCNT		; Any nop's to send?
	 JRST IOUNOP		; Yes, go send them
   IFN TCPF,<
	HLLZS TNBFFL		; Assume out buf will be NCP owned
   >
	MOVE T1,IMPHBO		; Hi priority msg waiting?
	JUMPE T1,IMPIOT		; No, check lo priority
	HLRZ T2,0(T1)		; Does it have a successor?
	JUMPN T2,IMPIO1		; Jump if so
	SETZM IMPHBI		; If not, say no more to go
	SKIPA			; And don't add network section
IMPIO1:	HRLI T2,ANBSEC		; Section buffers are in
	MOVEM T2,IMPHBO		; For next removal
IFN BBNF,<SETZM OUTMSG>		; SAY NOT DOING TELENET
	JRST IMPIOC		; Send buffer in T1

IMPIOT:
   REPEAT 0,< ;Until TCP done
	; Select either a TCP buffer or low priority NCP buffer
	; for output.  Either of these will give credit to the
	; other.  When both are present, it is the one with the
	; most credit that is used.  This prevents one from
	; strangling the other in high traffic situations.

	HLRZ T1,TCPOBO
	JUMPE T1,IMPIOL		; No TCP waiting.  Go check NCP low pri.
	HLRZ T1,IMPOBO
	JUMPE T1,IMPIOO		; Jump if only TCP output waiting
	SKIPG TCPNCP		; Both waiting.  Which gets it?
	 JRST IMPIOZ		; NCP
	HRRZ T1,TNPRIO		; Output from TCP. Credit NCP.
	MOVNS T1
	ADDM T1,TCPNCP		; More negative to favor NCP
IMPIOO:	HLRZ T1,TCPOBO		; TCP message for output
	HLLZ T2,0(T1)		; Get its successor
	JUMPN T2,.+3		; Jump if not last one
	MOVEI T3,TCPOBO
	MOVEM T3,TCPOBI
	MOVEM T2,TCPOBO
	HLLOS TNBFFL		; Remember out buf is TCP owned
IFN BBNF,<SETZM OUTMSG>		; SAY NOT DOING TELENET
	JRST IMPIOC

TNPRIO:	1,,3	; Diddlable constant: TCP,,NCP favoritism

IMPIOZ:	HLRZ T1,TNPRIO		; Get amount of credit for TCP
	ADDM T1,TCPNCP		; More positive to favor TCP next time
   > ;End repeat 0 for TCP
IMPIOL:	MOVE T1,IMPOBO		; Msg waiting to go out?

IFN BBNF,<JUMPN T1,IMPIOY	; YES - DO IT
	MOVE T1,OUTREQ>		; NO - TELENET BUFFER TO DO?

	JUMPE T1,[SKIPE T2,HSTGDM ; NO - HOST GOING DOWN?
		 JRST IOUHGD	; Send the host going down msg
		CONO ANO,0	; NONE TO SEND. TURN OFF OUTPUT.
		MOVE T1,[MSEC1,,IMODN2] ; DISPATCH WHEN IT IS TURNED ON
		MOVEM T1,IMODSP	; ..
		SETZM IMPOB
		RET]
IFN BBNF,<SETZM OUTREQ		; DO TELENET BUFFER, CLEAR REQUEST
	MOVEM T1,OUTMSG	; IT IS ACTIVE TELENET MSG
	ADDI T1,1		; TNB.OS, OFFSET TO ARPANET FORMAT
	JRST IMPIOC>		; SEND IT

IMPIOY:	HLRZ T2,0(T1)		; Get bfr
	JUMPN T2,IMPIO2
	SETZM IMPOBI		; None to go after this one
	SKIPA			; And leave off section number
IMPIO2:	HRLI T2,ANBSEC		; Set buffer's section
	MOVEM T2,IMPOBO

IFN BBNF,<SETZM OUTMSG>		; SAY NOT DOING TELENET

IMPIOC:	MOVEM T1,IMPOB
	SETZRO NBQUE,(T1)	; DeQueue buffer from its old chain
;Now decide on packing via message type
IFN BBNF,<
	LOAD T2,IHLNK,(T1)	;Check for MLC OR TELENET traffic
	CAIN T2,TNTLNK		;IS IT TELENET LINK?
	 JRST [ MOVEI T3,.IITNT	;YES. - PACK APPROPRIATELY
		JRST IMPIOD]
	LSH T2,-1
	CAMN T2,MLCHLF		;PTIP link?
	JRST [	MOVEI T3,.IIMLC	;Yes. pack in 36 bit mode
		JRST IMPIOD]
   IFN TCPF,<
	HRRE T2,TNBFFL		; See who owns the out buffer
   >
	JUMPL T2,[MOVEI T3,.IIINT	; TCP.  Set packing mode
		JRST IMPIOD]
>
	LOAD T2,IHHST,(T1)	;Check host and link for NCP range
	LOAD T3,IHLNK,(T1)	; ..
	CAIGE T2,FKHOST		;Special to-imp group?
	CAILE T3,LLINK		;Or link out of range?
	JRST [	MOVEI T3,.IISPQ	;Yes, special queue formatting.
		JRST IMPIOD]
	LOAD T2,HHSIZ,(T1)	;NCP will have set up packing mode
	CAIE T2,^D36		;Is it 36 bit mode?
	SKIPA T3,[.IINC2]	;No, it is 8 or 32.
	MOVEI T3,.IINC6		;Select 36 bit mode
IMPIOD:	MOVE T2,[MSEC1,,IMOLDR]	;Where to go on next interrupt
	MOVEM T2,IMODSP		; ..
	MOVEM T3,IMOTYP		;Remember packing type decision
	MOVEI T2,.NBLD0(T1)	;First word to send out
	HRLI T2,(<.NBLD2+1>B12)	;Send first three words and some fills
	TLO T2,ANBSEC		;From this section
	CONO ANO,ANXWAR		; Select word-count and addr register
	DATAO ANO,T2		; Tell it what to send
	CONO ANO,ANOM36+ANOBSY+ANOCLE+ANXCHS	; Send it in 36-bit mode
	RET			; Done with start-up-output routine
; Here at PI level when leader and first fill word have been sent.
; No AC's saved yet. Now re-send some more fill, and send H-H leader.

IMOLDR:	DMOVEM T1,IMPIAC+T1	;Save standard interrupt level AC's
	DMOVEM T3,IMPIAC+T3	; ..
	DMOVEM CX,IMPICX	; ..
	MOVE P,PIMSTK		; And set up a local PI level stack
	MOVE T1,[MSEC1,,IMOLD3]	;Where to come on next interrupt
	MOVEM T1,IMODSP		; ..
	MOVE T1,IMPOB		;Buffer we are working on
	MOVE T4,IMOTYP		;Get the packing control
	MOVEI T2,.NBHHL-1(T1)	;Resend another word as pads, then H-H leader
	HLL T2,II1WCT(T4)	;Set up right count
	TLO T2,ANBSEC		;In the right section
	DATAO ANO,T2		;Send those words
	LOAD T3,NBBSZ,(T1)	;That might be all. Check size of buffer
	CAILE T3,.NBHHL		;Just that much?
	TDZA T2,T2		;There's more than that.
	MOVEI T2,ANOEND		;That's all. Include End of Msg bit
	IOR T2,IO1CNO(T4)	;Plus the right word size, etc.
	CONO ANO,0(T2)
	JRST IMPUBO		;Finished that output interrupt.

IO1CNO:	ANOM36+ANOBSY+ANXCHS	;NCP 36 BIT MODE
	ANOM36+ANOBSY+ANXCHS	;NCP 32 BIT MODE
	ANOM36+ANOBSY+ANXCHS	;TELENET MODE
	ANOBSY+ANXCHS		;SPECIAL QUEUES
	ANOBSY+ANXCHS		;Internet MODE
	ANOM36+ANOBSY+ANXCHS	;MLC/PTIP MODE
	ANOM36+ANOBSY+ANXCHS	;Not referenced here

IO2CNO:	ANOM36+ANOEND+ANOBSY+ANXCHS	;NCP 36 BIT MODE
	ANOEND+ANOBSY+ANXCHS		;NCP 32 BIT MODE
	ANOM36+ANOEND+ANOBSY+ANXCHS	;TELENET MODE
	ANOEND+ANOBSY+ANXCHS		;SPECIAL QUEUES
	ANOEND+ANOBSY+ANXCHS		;Internet MODE
	ANOM36+ANOEND+ANOBSY+ANXCHS	;MLC/PTIP MODE
	ANOM36+ANOEND+ANOBSY+ANXCHS	;Not referenced here
;Here after completing the above, again on PI level. If more
; words to send, set them up.

IMOLD3:	CONSZ ANO,ANODON	;Was it a short message?
	JRST IMODN0		;Yes, go wrap up. Release buffer, etc.
	DMOVEM T1,IMPIAC+T1	;Save standard interrupt level AC's
	DMOVEM T3,IMPIAC+T3	; ..
	DMOVEM CX,IMPICX	; ..
	MOVE P,PIMSTK		; And set up a local PI level stack
	MOVE T1,IMPOB		;Buffer we have been sending
	MOVE T4,IMOTYP		;Get the packing control
	LOAD T2,NBBSZ,(T1)	;How many words in it?
	MOVE T3,II2LDT(T4)	;How far we have done so far
	SUBI T2,0(T3)		;Less those sent above
	LSH T2,^D<35-12>	;Position for AN10 word count
	HRR T2,T1		;Next word to go out.
	ADDI T2,0(T3)		; ..
	TLO T2,ANBSEC		;In the buffer section
	MOVEM T2,IMPOUP
	DATAO ANO,IMPOUP	;Tell it what data to send
	HRRZ T3,IO2CNO(T4)	;Bits for CONO
	CONO ANO,0(T3)		;And make it go
	MOVE T3,[MSEC1,,IMODN0]	;When done, we will release the buffer
	MOVEM T3,IMODSP		; ..
	JRST IMPUBO		;Now dismiss this interrupt.
;Here to make a Host Going Down message

IOUHGD:	MOVEI T3,0		;Build the message in 2 and 3
	LSHC T2,-^D8
	DMOVEM T2,IIMBUF+1	;And use the special irreg msg buffer
	MOVE T2,H2IHGD		;Pattern for message type
	MOVEM T2,IIMBUF		; ..
	MOVEI T2,IIMBUF		;Now send this to IMP
	JRST IOUIRG		;Go send it

IOUNOP:	SOS NOPCNT
	MOVEI T2,H2INOP		;Send a NOP message
IOUIRG:	HRLI T2,(<.NBLD2>B12)	;Length of the msg
	CONO ANO,ANXWAR		; SET FOR WD CT / ADDR REGISTER
	TLO T2,MSEC1		;These consts and temps are in mon section
	DATAO ANO,T2		;Send the irreg message
	CONO ANO,ANOM36+ANOBSY+ANOEND+ANXCHS	;Start it, 36-bit mode
	MOVE T1,[MSEC1,,IMODN2]	;When done, no buffer to release
	MOVEM T1,IMODSP
	RET

;Prototypes of the two H2I irreg messages we ever send.
;The NOP message has the padding control in it.

H2INOP:	BYTE (4)0,ITY%LL (16)0 (8).IHNOP (4)0
	EXP 0
	BYTE (4)0,STY%NP

H2IHGD:	BYTE (4)0,ITY%LL (16)0 (8).IHHGD (4)0
;;	BYTE (4)0 (24)0 (3)DayOfWeek (5)Hour
;;	BYTE (4)5MinPeriod, Reason
; Pi service for output

;HERE AFTER "OUT DONE" INTERRUPT FOR A REAL BUFFER

IMODN0:	DMOVEM T1,IMPIAC+T1	; Save standard interrupt level AC's
	DMOVEM T3,IMPIAC+T3	; ..
	DMOVEM CX,IMPICX	; ..
	MOVE P,PIMSTK		; And set up a local PI level stack
	CALL IMODUN		; POST COMPLETION, FREE THE BUFFER
	MOVE T1,IMPOB
	CALL IMULKB		; Unlock bfr

IMPDO4:	SETZM IMPOB		; Mark no output in progress
	CALL IMPIOU		; Start next msg if any
IMPUBO:	DMOVE T1,IMPIAC+T1	; Restore AC's from before PI
	DMOVE T3,IMPIAC+T3
	DMOVE CX,IMPICX
	XJEN ANOVI1		; AND DISMISS INTERRUPT

;HERE AFTER "OUT DONE" INTERRUPT WHEN NO BUFFER TO RELEASE.

IMODN2:	DMOVEM T1,IMPIAC+T1	; Save standard interrupt level AC's
	DMOVEM T3,IMPIAC+T3	; ..
	DMOVEM CX,IMPICX	; ..
	MOVE P,PIMSTK		; And set up a local PI level stack
	JRST IMPDO4
;STATUS CHECK SUBROUTINES

IMPRLQ::PUSH P,T1		;SAVE AN AC
	CONI ANI,T1		;GET CURRENT STATUS
	TLNE T1,(1B4+1B5)	;IS IT POWERED UP, WITH A CABLE IN IT?
	TRNE T1,ANIIID		;YES. IS READY LINE ALSO OK?
	SKIPA			;NO, IT ISN'T READY.
	AOS -1(P)		;ALL IS WELL. SKIP RETURN.
	JRST PA1		;RESTORE AC1 AND RETURN

;HERE FROM DOWN-SEQUENCE PROCESSING IN NCPFRK TO COMPLETELY
; SHUT OFF THE HARDWARE DEVICE

IDVKIL::CONO ANO,0		;TURN OFF OUTPUT SIDE
	CONO ANI,ANIRST		;CLEAR DEVICE
	CONO ANI,ANXVAR		;HAVE TO POINT TO WHERE HOST READY IS
	DATAO ANI,[<0*ANIHRL>+MSEC1B+ANIVIL]	;CLEAR READY, LEAVE
				; LEAVE INTERRUPT ADDRESS ALONE.
	RET

;CALL HERE FROM IMPIN0 (ONLY FROM NCPFRK) AT INITIALIZATION OF
; BACKGROUND FORK - NOT ON EVERY RECYCLE OF READY LINE.

IMPRSD::MOVE T1,[MSEC1,,IMIN0X]	;RESET DISPATCHES
	MOVEM T1,IMIDSP		;INPUT PI DISPATCH TO SHUT OFF DEVICE
	MOVE T1,[MSEC1,,IMODN2]	;OUTPUT PI DISPATCH TO START NEW MSG
	MOVEM T1,IMODSP
	RET
;CALL HERE FROM NCPFRK, PROCESS LEVEL, WHEN IMP IS WANTED UP
; BUT NET IS CURRENTLY DOWN.

IMPRSS::CALL IMPRLQ		; IS IMP ON AND READY?
	 RET			; No, stop here
	CALL IMPRSN		; Reset variables
	SETZM IMPRDL		; And notices of IMP ERROR
	CONO ANI,ANIRST		; CLEAR THE DEVICE
	CONO ANI,ANXVAR+ANICLE	; SET VECTOR ADDRESS WORDS
	DATAO ANI,[ANIHRL+MSEC1B+ANIVIL]	; SET THE HOST READY LINE
	CONO ANO,ANOCLE+ANXVAR	; SAME FOR OUTPUT
	DATAO ANO,[MSEC1,,ANOVIL] ; VECTOR INT LOCATION FOR OUTPUT
	SETZM IMPDRQ		; Forget any intervening down requests
	MOVNI T1,2
	MOVEM T1,IMPFLS		; Init flush count
	MOVEI T1,3
	MOVEM T1,NOPCNT
	MOVEI T1,^D1000
	DISMS			; Allow time for ready line to settle
	AOS NETTCH		; Cause change in state to be noted
	AOS JB0FLG
	GTAD			; Yes
	MOVEM T1,NCPUPT		; Save time whe it came up
	CONO ANO,ANOBSY+ANXCHS	; TELL OUTPUT SIDE TO GO.
	SKIPLE IMPNFI		; If input bfrs available,
	 CALL IMISRT		; Start input
	SETOM IMPRDY
	SETOM IMPORD		; Allow output
	MOVE T1,NLHOST		; Local host
	CALL IMPRRP		; Send ourselves an rrp
	RET

;Dummy routine to init IMP interface

IMPINI::RET

IMPFPF::			; ROUTINE TO DETERMINE IF AN10/20 CAUSED
				; AN IOPGF....PAGE NUMBER IS IN T1
	CONO ANI,ANXWAR		; SELECT INPUT SIDE WORD ADR REG.
	DATAI ANI,T2		; GET THE WORD ADR REGISTER CONTENTS
	CONO ANO,ANXWAR		; SELECT OUTPUT SIDE WORD ADR REG.
	DATAI ANO,T3		; GET THE WORD ADR REGISTER CONTENTS
	LOAD T2,VPGNO,T2	; GET THE PAGE NUMBER INPUT WORKING ON
	LOAD T3,VPGNO,T3	; GET THE PAGE NUMBER OUTPUT WORKING ON
	CAME T1,T2		; INPUT SIDE CAUSE IOPGF?
	 CAMN T1,T3		; OUTPUT SIDE CAUSE IOPGF?
	  SKIPA			; YES
	   RET			; NO WE DID NOT CAUSE IT
	CALL IDVKIL		; WE CAUSED IOPGF SO SHUT OFF DEVICE
	BUG(IMPIOP)		; TELL THE WORLD WE CAUSED IT
	JRST RSKP		; SKIP RETURN TO CALLER

	TNXEND
	END ; OF IMPPHY