; EmuEIAMRT.mu -- MRT modified to poll Alto EIA interface and
;			invoke emulator-level processing when needed

;	Last modified September 3, 1978  2:05 PM

; **** Memory Refresh task ****
; This is the MRT for Alto IIs with Extended Memory (16K chips).
; It is modified to abolish the Interval Timer, to eliminate CLOCKTEMP,
; and to send control to the EIA code if turned on (R37[15] = 1).

!17,20,TX0,TX6,TX3,TX2,TX8,TX5,TX1,TX7,TX4,,,,,,,;
!1,2,PollEIA, NoEIA;
!1,2,~EIARq, EIARq;
!1,2,EIAInt, EIAExit;
!1,2,DOCUR,NOCUR;
!1,2,SHOWC,WAITC;

!1,2,NOCLK,CLOCK;
!1,1,MRTLAST;
!1,2,CNOTLAST,CLAST;

$CURX		$R20;
$CURDATA	$R21;
$MTEMP		$R25;
$YPOS		$R27;
$R37		$R37;
$NWW		$R4;
$REFIIMSK	$7777;

; This version assumes MRTACT is cleared by BLOCK, not MAR_ R37
; R37 [4-13] are the low bits of the TOD clock
; R37 [8-14] are the refresh address bits
; Each time MRT runs, four refresh addresses are generated, though
; R37 is incremented only once.  Sprinkled throughout the execution
; of this code are the following operations having to do with refresh:
;	MAR_ R37
;	R37_ R37 +4		NOTE THAT R37 [14] DOES NOT CHANGE
;	MAR_ R37 XOR 2		TOGGLES BIT 14
;	MAR_ R37 XOR 200	TOGGLES BIT 8
;	MAR_ R37 XOR 202	TOGGLES BITS 8 AND 14

MRT:	MAR_ R37;		**FIRST REFRESH CYCLE**
	SINK_ MOUSE, BUS;	MOUSE DATA IS ANDED WITH 17B
MRTA:	L_ T_ -2, :TX0;		DISPATCH ON MOUSE CHANGE
TX0:	L_ R37 AND NOT T, T_ R37;INCREMENT CLOCK
	T_ 3+T+1, SH=0;		IE. T_ T +4.  IS INTV TIMER ON?
	L_ REFIIMSK AND T, :PollEIA; [PollEIA, NoEIA] ZERO HIGH 4 BITS
NoEIA:	R37_ L; 		STORE UPDATED CLOCK
~EIARq:	T_ 2;			NO STATE AT THIS POINT IN PUBLIC REGS
	MAR_ R37 XOR T,T_ R37;	**SECOND REFRESH CYCLE**
	L_ REFZERO AND T;	ONLY THE CLOKCK BITS, PLEASE
	SH=0, TASK;		TEST FOR CLOCK OVERFLOW
	:NOCLK;			[NOCLK,CLOCK]
NOCLK:	T _ 200;
	MAR_ R37 XOR T;		**THIRD FEFRESH CYCLE**
	L_ CURX, BLOCK;		CLEARS WAKEUP REQUEST FF
	T_ 2 OR T, SH=0;	NEED TO CHECK CURSOR?
	MAR_ R37 XOR T, :DOCUR;	**FOURTH REFRESH CYCLE**
NOCUR:	CURDATA_ L, TASK;
MRTLAST:CURDATA_ L, :MRT;	END OF MAIN LOOP

; Memory Refresh Task (cont'd)

CLOCK:	MAR_ CLOCKLOC;		R37 OVERFLOWED.
	NOP;
	L_ MD+1;		INCREMENT CLOCK IM MEMORY
	MAR_ CLOCKLOC;
	MTEMP_ L, TASK;
	MD_ MTEMP, :NOCLK;

DOCUR:	L_ T_ YPOS;		CHECK FOR VISIBLE CURSOR ON THIS SCAN
	SH<0, L_ 20-T-1;	 ***x13 change: the constant 20 was 17
	SH<0, L_ 2+T, :SHOWC;	[SHOWC,WAITC]

WAITC:	YPOS_ L, L_ 0, TASK, :MRTLAST;	SQUASHES PENDING BRANCH
SHOWC:	MAR_ CLOCKLOC+T+1, :CNOTLAST;

CNOTLAST: T_ CURX, :CURF;
CLAST:	T_ 0;
CURF:	YPOS_ L, L_ T;
	CURX_ L;
	L_ MD, TASK;
	CURDATA_ L, :MRT;


;AFTER THIS DISPATCH, T WILL CONTAIN XCHANGE, L WILL CONTAIN YCHANGE-1

TX1:	L_ T_ ONE +T, :M00;		Y=0, X=1
TX2:	L_ T_ ALLONES, :M00;		Y=0, X=-1
TX3:	L_ T_ 0, :M00;			Y=1, X=0
TX4:	L_ T_ ONE AND T, :M00;		Y=1, X=1
TX5:	L_ T_ ALLONES XOR T, :M00;	Y=1, X=-1
TX6:	T_ 0, :M00;			Y=-1, X=0
TX7:	T_ ONE, :M00;			Y=-1, X=1
TX8:	T_ ALLONES, :M00;		Y=-1, X=-1

M00:	MAR_ MOUSELOC;			START THE FETCH OF THE COORDINATES
	MTEMP_ L;			YCHANGE -1
	L_ MD+ T;			X+ XCHANGE
	T_ MD;				Y
	MAR_ MOUSELOC;			NOW RESTORE THE UPDATED COORDINATES
	T_ MTEMP+ T+1;			Y+ (YCHANGE-1) + 1
	MD_ M, L_ T, TASK;
	MD_ M, :MRTA;


; Here to poll the EIA interface.  If service is required,
; issue an interrupt on channel 16B and disable further polling.

PollEIA: MAR_ EIALOC;			EIALOC=0 if service is required
	R37_ L;				Store updated refresh address
	T_ 2;				Prepare to issue interrupt
	L_ NWW OR T;
	SINK_ MD, BUS=0;		Test EIALOC
	T_ R37-1, :~EIARq;		[~EIARq, EIARq]

EIARq:	NWW_ L, L_ T, TASK, :NoEIA;	Issue interrupt, R37[15]_ 0