;-----------------------------------------------------------------;
; X M E S A M I C R O C O D E ;
; Version 39-3 ;
;-----------------------------------------------------------------;
; MesaROM.Mu - Instruction fetch and general subroutines
; Last modified by Levin - March 6, 1979 10:40 AM
; 'uCodeVersion' is used by RunMesa to determine what version of the Mesa microcode is
; in ROM1. This version number should be incremented by 1 for every official release of
; the microcode. 'uCodeVersion' is mapped by RunMesa to the actual version number (which
; appears as a comment above). The reason for this mapping is the limited number of
; constants in the Alto constants ROM, otherwise, we would obviously have assigned
; 'uCodeVersion' the true microcode version number.
;
; The current table in RunMesa should have the following correspondences:
; uCodeVersion Microcode version Mesa release
; 0 34 4.1
; 1 39 5.0
$uCodeVersion $1;
;Completely rewritten by Roy Levin, Sept-Oct. 1977
;Modified by Johnsson; July 25, 1977 10:20 AM
;First version assembled 5 June 1975.
;Developed from Lampson's MESA.U of 21 March 1975.
;-----------------------------------------------------------------
; GLOBAL CONVENTIONS AND ASSUMPTIONS
;-----------------------------------------------------------------
; 1) Stack representation:
; stkp=0 => stack is empty
; sktp=10 => stack is full
; The validity checking that determines if the stack pointer is
; within this range is somewhat perfunctory. The approach taken is
; to include specific checks only where there absence would not lead
; to some catastrophic error. Hence, the stack is not checked for
; underflow, since allowing it to become negative will cause a disaster
; on the next stack dispatch.
; 2) Notation:
; Instruction labels correspond to opcodes in the obvious way. Suffixes
; of A and B (capitalized) refer to alignment in memory. 'A' is intended
; to suggest the right-hand byte of a memory word; 'B' is intended to
; suggest the left-hand byte. Labels terminating in a lower-case letter
; generally name local branch points within a particular group of
; opcodes. (Exception: subroutine names.) Labels terminating in 'x' generally
; exist only to satisfy alignment requirements imposed by various dispatches
; (most commonly IR← and B/A in instruction fetch).
; 3) Tasking:
; Every effort has been made to ensure that a 'TASK' appears approximately
; every 12 instructions. Occasionally, this has not been possible,
; but (it is hoped that) violations occur only in infrequently executed
; code segments.
; 4) New symbols:
; In a few cases, the definitions of the standard Alto package
; (AltoConsts23.MU) have not been quite suitable to the needs of this
; microcode. Rather than change the standard package, we have defined
; new symbols (with names beginning with 'm') that are to be used instead
; of their standard counterparts. All such definitions appear together in
; Mesab.Mu.
; 5) Subroutine returns:
; Normally, subroutine returns using IDISP require one to deal with
; (the nuisance of) the dispatch caused by loading IR. Happily, however,
; no such dispatch occurs for 'msr0' and 'sr1' (the relevant bits
; are 0). To cut down on alignment restrictions, some subroutines
; assume they are called with only one of two returns and can
; therefore ignore the possibility of a pending IR← dispatch.
; Such subroutines are clearly noted in the comments.
; 6) Frame pointer registers (lp and gp):
; These registers normally (i.e. except during Xfer) contain the
; addresses of local 2 and global 1, respectively. This optimizes accesses
; in such bytecodes as LL3 and SG2, which would otherwise require another cycle.
;-----------------------------------------------------------------
; Get definitions for ALTO and MESA
;-----------------------------------------------------------------
#AltoConsts23.mu;
#MesabROM.mu;
;-----------------------------------------------------------------
; Location-specific Definitions
;-----------------------------------------------------------------
; There is a fundamental difficulty in the selection of addresses that are known and
; used outside the Mesa emulator. The problem arises in trying to select a single set of
; addresses that can be used regardless of the Alto's control memory configuration. In
; effect, this cannot be done. If an Alto has only a RAM (in addition, of course, to its
; basic ROM, ROM0), then the problem does not arise. However, suppose the Alto has both a
; RAM and a second ROM, ROM1. Then, when it is necessary to move from a control memory to
; one of the other two, the choice is conditioned on (1) the memory from which the transfer
; is occurring, and (2) bit 1 of the target address. Since we expect that, in most cases, an
; Alto running Mesa will have the Mesa emulator in ROM1, the externally-known addresses have
; been chosen to work in that case. They will also work, without alteration, on an Alto that
; has no ROM1. However, if it is necessary to run Mesa on an Alto with ROM1 and it is desired
; to use a Mesa emulator residing in the RAM (say, for debugging purposes), then the address
; values in the RAM version must be altered. This implies changes in both the RAM code itself
; and the Nova code that invokes the RAM (via the Nova JMPRAM instruction). Details
; concerning the necessary changes for re-assembly appear with the definitions below.
; Note concerning Alto IVs and Alto IIs with retrofitted 3K control RAMs:
;
; The above comments apply uniformly to these machines if "RAM" is systematically replaced
; by "RAM1" and "ROM1" is systematically replaced by "RAM2".
%1,1777,0,nextBa; forced to location 0 to save a word in JRAM
;-----------------------------------------------------------------
; Emulator Entry Point Definitions
; These addresses are known by the Nova code that interfaces to the emulator and by
; RAM code executing with the Mesa emulator in ROM1. They have been chosen so that
; both such "users" can use the same value. Precisely, this means that bit 1 (the
; 400 bit) must be set in the address. In a RAM version of the Mesa emulator intended
; to execute on an Alto with a second ROM, bit 1 must be zero.
;-----------------------------------------------------------------
%1,1777,420,Mgo; Normal entry to Mesa Emulator - load state
; of process specified by AC0.
%1,1777,400,next,nextA; Return to 'next' to continue in current Mesa
; process after Nova or RAM execution.
$Minterpret $L004400,0,0; Documentation refers to 'next' this way.
%1,1777,776,DSTr1,Mstopc; Return addresses for 'Savestate'. By
; standard convention, 'Mstopc' must be at 777.
;-----------------------------------------------------------------
; Linkage from RAM to ROM1
; The following predefs must correspond to the label definitions in MesabROM.mu
;-----------------------------------------------------------------
%1,1777,406,Intstop; must correspond to romIntstop
%1,1777,407,Untail; must correspond to romUntail
%7,1777,430,XferGT,Xfer,Mstopr,PORTOpc,LSTr,ALLOCrfr; Xfer must agree with romXfer
;-----------------------------------------------------------------
; Linkage from Mesa emulator to ROM0
; The Mesa emulator uses a number of subroutines that reside in ROM0. In posting a
; return address, the emulator must be aware of the control memory in which it resides,
; RAM or ROM1. These return addresses must satisfy the following constraint:
; no ROM1 extant or emulator in ROM1 => bit 1 of address must be 1
; ROM1 extant and emulator in RAM => bit 1 of address must be 0
; In addition, since these addresses must be passed as data to ROM0, it is desirable
; that they be available in the Alto's constants ROM. Finally, it is desirable that
; they be chosen not to mess up too many pre-defs. It should be noted that these
; issues do not affect the destination location in ROM0, since its address remains
; fixed (even with respect to bit 1 mapping) whether the Mesa emulator is in RAM or
; ROM1. [Note pertaining to Alto IVs and retrofitted Alto IIs with 3K RAMs: to avoid
; confusion, the comments above and below have not been revised to discuss 3K control
; RAMs. In all cases, there is an additional constraint that bit 2 of the return
; addresses must be 1. The suggested values observe this constraint, even though the
; comments do not explicitly mention it.]
;-----------------------------------------------------------------
;-----------------------------------------------------------------
; MUL/DIV linkage:
; An additional constraint peculiar to the MUL/DIV microcode is that the high-order
; bits of the return address be 1's. Hence, the recommended values are:
; no ROM1 extant or emulator in ROM1 => MULDIVretloc = 177675B (OK to be odd)
; ROM1 extant and emulator in RAM => MULDIVretloc = 177162B (OK to be odd)
;-----------------------------------------------------------------
$ROMMUL $L004120,0,0; MUL routine address (120B) in ROM0
$ROMDIV $L004121,0,0; DIV routine address (121B) in ROM0
$MULDIVretloc $177675; (may be even or odd)
; The third value in the following pre-def must be: (MULDIVretloc AND 777B)
%1,1777,675,MULDIVret,MULDIVret1; return addresses from MUL/DIV in ROM0
;-----------------------------------------------------------------
; BITBLT linkage:
; An additional constraint peculiar to the BITBLT microcode is that the high-order
; bits of the return address be 1's. Hence, the recommended values are:
; no ROM1 extant or emulator in ROM1 => BITBLTret = 177714B
; ROM1 extant and emulator in RAM => BITBLTret = 177175B
;-----------------------------------------------------------------
$ROMBITBLT $L004124,0,0; BITBLT routine address (124B) in ROM0
$BITBLTret $177714; (may be even or odd)
; The third value in the following pre-def must be: (BITBLTret AND 777B)-1
%1,1777,713,BITBLTintr,BITBLTdone; return addresses from BITBLT in ROM0
;-----------------------------------------------------------------
; CYCLE linkage:
; A special constraint here is that WFretloc be odd. Recommended values are:
; no ROM1 extant or emulator in ROM1 => Fieldretloc = 612B, WFretloc = 605B
; ROM1 extant and emulator in RAM => Fieldretloc = 34104B, WFretloc = 14023B
;-----------------------------------------------------------------
$RAMCYCX $L004022,0,0; CYCLE routine address (22B) in ROM0
$Fieldretloc $612; RAMCYCX return to Fieldsub (even or odd)
$WFretloc $605; RAMCYCX return to WF (must be odd)
; The third value in the following pre-def must be: (Fieldretloc AND 1777B)
%1,1777,612,Fieldrc; return address from RAMCYCX to Fieldsub
; The third value in the following pre-def must be: (WFretloc AND 1777B)-1
%1,1777,604,WFnzct,WFret; return address from RAMCYCX to WF
;-----------------------------------------------------------------
; I n s t r u c t i o n f e t c h
;
; State at entry:
; 1) ib holds either the next instruction byte to interpret
; (right-justified) or 0 if a new word must be fetched.
; 2) control enters at one of the following points:
; a) next: ib must be interpreted
; b) nextA: ib is assumed to be uninteresting and a
; new instruction word is to be fetched.
; c) nextXB: a new word is to be fetched, and interpretation
; is to begin with the odd byte.
; d) nextAdeaf: similar to 'nextA', but does not check for
; pending interrupts.
; e) nextXBdeaf: similar to 'nextXB', but does not check for
; pending interrupts.
;
; State at exit:
; 1) ib is in an acceptable state for subsequent entry.
; 2) T contains the value 1.
; 3) A branch (1) is pending if ib = 0, meaning the next
; instruction may return to 'nextA'. (This is subsequently
; referred to as "ball 1", and code that nullifies its
; effect is labelled as "dropping ball 1".)
; 4) If a branch (1) is pending, L = 0. If no branch is
; pending, L = 1.
;-----------------------------------------------------------------
;-----------------------------------------------------------------
; Address pre-definitions for bytecode dispatch table.
;-----------------------------------------------------------------
; Table must have 2 high-order bits on for BUS branch at 'nextAni'.
;
; Warning! Many address inter-dependencies exist - think (at least) twice
; before re-ordering. Inserting new opcodes in previously unused slots,
; however, is safe.
; XMESA Note: RBL, WBL, and BLTL exist for XMESA only.
%7,1777,1400,NOOP,ME,MRE,MXW,MXD,NOTIFY,BCAST,REQUEUE; 000-007
%7,1777,1410,LL0,LL1,LL2,LL3,LL4,LL5,LL6,LL7; 010-017
%7,1777,1420,LLB,LLDB,SL0,SL1,SL2,SL3,SL4,SL5; 020-027
%7,1777,1430,SL6,SL7,SLB,PL0,PL1,PL2,PL3,LG0; 030-037
%7,1777,1440,LG1,LG2,LG3,LG4,LG5,LG6,LG7,LGB; 040-047
%7,1777,1450,LGDB,SG0,SG1,SG2,SG3,SGB,LI0,LI1; 050-057
%7,1777,1460,LI2,LI3,LI4,LI5,LI6,LIN1,LINI,LIB; 060-067
%7,1777,1470,LIW,LINB,LADRB,GADRB,,,,; 070-077
%7,1777,1500,R0,R1,R2,R3,R4,RB,W0,W1; 100-107
%7,1777,1510,W2,WB,RF,WF,RDB,RD0,WDB,WD0; 110-117
%7,1777,1520,RSTR,WSTR,RXLP,WXLP,RILP,RIGP,WILP,RIL0; 120-127
%7,1777,1530,WS0,WSB,WSF,WSDB,RFC,RFS,WFS,RBL; 130-137
%7,1777,1540,WBL,,,,,,,; 140-147
%7,1777,1550,,,,,,,,; 150-157
%7,1777,1560,,,SLDB,SGDB,PUSH,POP,EXCH,LINKB; 160-167
%7,1777,1570,DUP,NILCK,,BNDCK,,,,; 170-177
%7,1777,1600,J2,J3,J4,J5,J6,J7,J8,J9; 200-207
%7,1777,1610,JB,JW,JEQ2,JEQ3,JEQ4,JEQ5,JEQ6,JEQ7; 210-217
%7,1777,1620,JEQ8,JEQ9,JEQB,JNE2,JNE3,JNE4,JNE5,JNE6; 220-227
%7,1777,1630,JNE7,JNE8,JNE9,JNEB,JLB,JGEB,JGB,JLEB; 230-237
%7,1777,1640,JULB,JUGEB,JUGB,JULEB,JZEQB,JZNEB,,JIW; 240-247
%7,1777,1650,ADD,SUB,MUL,DBL,DIV,LDIV,NEG,INC; 250-257
%7,1777,1660,AND,OR,XOR,SHIFT,DADD,DSUB,DCOMP,DUCOMP; 260-267
%7,1777,1670,ADD01,,,,,,,; 270-277
%7,1777,1700,EFC0,EFC1,EFC2,EFC3,EFC4,EFC5,EFC6,EFC7; 300-307
%7,1777,1710,EFC8,EFC9,EFC10,EFC11,EFC12,EFC13,EFC14,EFC15; 310-317
%7,1777,1720,EFCB,LFC1,LFC2,LFC3,LFC4,LFC5,LFC6,LFC7; 320-327
%7,1777,1730,LFC8,,,,,,,; 330-337
%7,1777,1740,,LFCB,SFC,RET,LLKB,PORTO,PORTI,KFCB; 340-347
%7,1777,1750,DESCB,DESCBS,BLT,BLTL,BLTC,,ALLOC,FREE; 350-357
%7,1777,1760,IWDC,DWDC,STOP,CATCH,MISC,BITBLT,STARTIO,JRAM; 360-367
%7,1777,1770,DST,LST,LSTF,,WR,RR,BRK,StkUf; 370-377
;-----------------------------------------------------------------
; Main interpreter loop
;-----------------------------------------------------------------
;
; Enter here to interpret ib. Control passes here to process odd byte of previously
; fetched word or when preceding opcode "forgot" it should go to 'nextA'. A 'TASK'
; should appear in the instruction preceding the one that branched here.
;
next: L←0, :nextBa; (if from JRAM, switch banks)
nextBa: SINK←ib, BUS; dispatch on ib
ib←L, T←0+1, BUS=0, :NOOP; establish exit state
;-----------------------------------------------------------------
; NOOP - must be opcode 0
; control also comes here from certain jump instructions
;-----------------------------------------------------------------
!1,1,nextAput;
NOOP: L←mpc+T, TASK, :nextAput;
;
; Enter here to fetch new word and interpret even byte. A 'TASK' should appear in the
; instruction preceding the one that branched here.
;
nextA: L←XMAR←mpc+1, :nextAcom; initiate fetch
;
; Enter here when fetch address has been computed and left in L. A 'TASK' should
; appear in the instruction that branches here.
;
nextAput: temp←L; stash to permit TASKing
L←XMAR←temp, :nextAcom;
;
; Enter here to do what 'nextA' does but without checking for interrupts
;
nextAdeaf: L←XMAR←mpc+1;
nextAdeafa: mpc←L, BUS=0, :nextAcomx;
;
; Common fetch code for 'nextA' and 'nextAput'
;
!1,2,nextAi,nextAni;
!1,2,nextAini,nextAii;
nextAcom: mpc←L; updated pc
SINK←NWW, BUS=0; check pending interrupts
nextAcomx: T←177400, :nextAi;
;
; No interrupt pending. Dispatch on even byte, store odd byte in ib.
;
nextAni: L←MD AND T, BUS, :nextAgo; L←"B"↑8, dispatch on "A"
nextAgo: ib←L LCY 8, L←T←0+1, :NOOP; establish exit state
;
; Interrupt pending - check if enabled.
;
nextAi: L←MD;
SINK←wdc, BUS=0; check wakeup counter
T←M.T, :nextAini; isolate left byte
nextAini: SINK←M, L←T, BUS, :nextAgo; dispatch even byte
;
; Interrupt pending and enabled.
;
!1,2,nextXBini,nextXBii;
nextAii: L←mpc-1; back up mpc for Savpcinframe
mpc←L, L←0, :nextXBii;
;
; Enter here to fetch word and interpret odd byte only (odd-destination jumps).
;
!1,2,nextXBi,nextXBni;
nextXB: L←XMAR←mpc+T;
SINK←NWW, BUS=0, :nextXBdeaf; check pending interrupts
;
; Enter here (with branch (1) pending) from Xfer to do what 'nextXB' does but without
; checking for interrupts. L has appropriate word PC.
;
nextXBdeaf: mpc←L, :nextXBi;
;
; No interrupt pending. Store odd byte in ib.
;
nextXBni: L←MD, TASK, :nextXBini;
nextXBini: ib←L LCY 8, :next; skip over even byte (TASK
; prevents L←0, :nextBa)
;
; Interrupt pending - check if enabled.
;
nextXBi: SINK←wdc, BUS=0, :nextXBni; check wakeup counter
;
; Interrupt pending and enabled.
;
nextXBii: ib←L, :Intstop; ib = 0 for even, ~= 0 for odd
;-----------------------------------------------------------------
; S u b r o u t i n e s
;-----------------------------------------------------------------
;
; The two most heavily used subroutines (Popsub and Getalpha) often
; share common return points. In addition, some of these return points have
; additional addressing requirements. Accordingly, the following predefinitions
; have been rather carefully constructed to accommodate all of these requirements.
; Any alteration is fraught with peril.
; [A historical note: an attempt to merge in the returns from FetchAB as well
; failed because more than 31D distinct return points were then required. Without
; adding new constants to the ROM, the extra returns could not be accommodated.
; However, for Popsub alone, additional returns are possible - see Xpopsub.]
;
; Return Points (sr0-sr17)
!17,20,Fieldra,SFCr,pushTB,pushTA,LLBr,LGBr,SLBr,SGBr,
LADRBr,GADRBr,RFr,Xret,INCr,RBr,WBr,Xpopret;
; Extended Return Points (sr20-sr37)
; Note: KFCr and EFCr must be odd!
!17,20,XbrkBr,KFCr,LFCr,EFCr,WSDBra,DBLr,LINBr,LDIVf,
Dpush,Dpop,RD0r,Splitcomr,RXLPrb,WXLPrb,MISCr,RWBLra;
; Returns for Xpopsub only
!17,20,WSTRrB,WSTRrA,JRAMr,WRr,STARTIOr,PORTOr,WD0r,ALLOCrx,
FREErx,NEGr,RFSra,RFSrb,WFSra,DESCBcom,RFCr,NILCKr;
; Extended Return Machinery (via Xret)
!1,2,XretB,XretA;
Xret: SINK←DISP, BUS, :XretB;
XretB: :XbrkBr;
XretA: SINK←0, BUS=0, :XbrkBr; keep ball 1 in air
;-----------------------------------------------------------------
; Pop subroutine:
; Entry conditions:
; Normal IR linkage
; Exit conditions:
; Stack popped into T and L
;-----------------------------------------------------------------
!1,1,Popsub; shakes B/A dispatch
!7,1,Popsuba; shakes IR← dispatch
!17,20,Tpop,Tpop0,Tpop1,Tpop2,Tpop3,Tpop4,Tpop5,Tpop6,Tpop7,,,,,,,;
Popsub: L←stkp-1, BUS, TASK, :Popsuba;
Popsuba: stkp←L, :Tpop; old stkp > 0
;-----------------------------------------------------------------
; Xpop subroutine:
; Entry conditions:
; L has return number
; Exit conditions:
; Stack popped into T and L
; Invoking instruction should specify 'TASK'
;-----------------------------------------------------------------
!1,1,Xpopsub; shakes B/A dispatch
Xpopsub: saveret←L;
Tpop: IR←sr17, :Popsub; returns to Xpopret
; Note: putting Tpop here makes
; stack underflow logic work if
; stkp=0
Xpopret: SINK←saveret, BUS;
:WSTRrB;
;-----------------------------------------------------------------
; Getalpha subroutine:
; Entry conditions:
; L untouched from instruction fetch
; Exit conditions:
; alpha byte in T
; branch 1 pending if return to 'nextA' desirable
; L=0 if branch 1 pending, L=1 if no branch pending
;-----------------------------------------------------------------
!1,2,Getalpha,GetalphaA;
!7,1,Getalphax; shake IR← dispatch
!7,1,GetalphaAx; shake IR← dispatch
Getalpha: T←ib, IDISP;
Getalphax: ib←L RSH 1, L←0, BUS=0, :Fieldra; ib←0, set branch 1 pending
GetalphaA: L←XMAR←mpc+1; initiate fetch
GetalphaAx: mpc←L;
T←177400; mask for new ib
L←MD AND T, T←MD; L: new ib, T: whole word
Getalphab: T←377.T, IDISP; T now has alpha
ib←L LCY 8, L←0+1, :Fieldra; return: no branch pending
;-----------------------------------------------------------------
; FetchAB subroutine:
; Entry conditions: none
; Exit conditions:
; T: <<mpc>+1>
; ib: unchanged (caller must ensure return to 'nextA')
;-----------------------------------------------------------------
!1,1,FetchAB; drops ball 1
!7,1,FetchABx; shakes IR← dispatch
!7,10,LIWr,JWr,,,,,,; return points
FetchAB: L←XMAR←mpc+1, :FetchABx;
FetchABx: mpc←L, IDISP;
T←MD, :LIWr;
;-----------------------------------------------------------------
; Splitalpha subroutine:
; Entry conditions:
; L: return index
; entry at Splitalpha if instruction is A-aligned, entry at
; SplitalphaB if instruction is B-aligned
; entry at Splitcomr splits byte in T (used by field instructions)
; Exit conditions:
; lefthalf: alpha[0-3]
; righthalf: alpha[4-7]
;-----------------------------------------------------------------
!1,2,Splitalpha,SplitalphaB;
!1,1,Splitx; drop ball 1
%160,377,217,Split0,Split1,Split2,Split3,Split4,Split5,Split6,Split7;
!1,2,Splitout0,Splitout1;
!7,10,RILPr,RIGPr,WILPr,RXLPra,WXLPra,Fieldrb,,; subroutine returns
Splitalpha: saveret←L, L←0+1, :Splitcom; L←1 for Getalpha
SplitalphaB: saveret←L, L←0, BUS=0, :Splitcom; (keep ball 1 in air)
Splitcom: IR←sr33, :Getalpha; T:alpha[0-7]
Splitcomr: L←17 AND T, :Splitx; L:alpha[4-7]
Splitx: righthalf←L, L←T, TASK; L:alpha, righthalf:alpha[4-7]
temp←L; temp:alpha
L←temp, BUS; dispatch on alpha[1-3]
temp←L LCY 8, SH<0, :Split0; dispatch on alpha[0]
Split0: L←T←0, :Splitout0; L,T:alpha[1-3]
Split1: L←T←ONE, :Splitout0;
Split2: L←T←2, :Splitout0;
Split3: L←T←3, :Splitout0;
Split4: L←T←4, :Splitout0;
Split5: L←T←5, :Splitout0;
Split6: L←T←6, :Splitout0;
Split7: L←T←7, :Splitout0;
Splitout1: L←10+T, :Splitout0; L:alpha[0-3]
Splitout0: SINK←saveret, BUS, TASK; dispatch return
lefthalf←L, :RILPr; lefthalf:alpha[0-3]
;-----------------------------------------------------------------
; D i s p a t c h e s
;-----------------------------------------------------------------
;-----------------------------------------------------------------
; Pop-into-T (and L) dispatch:
; dispatches on old stkp, so Tpop0 = 1 mod 20B.
;-----------------------------------------------------------------
Tpop0: L←T←stk0, IDISP, :Tpopexit;
Tpop1: L←T←stk1, IDISP, :Tpopexit;
Tpop2: L←T←stk2, IDISP, :Tpopexit;
Tpop3: L←T←stk3, IDISP, :Tpopexit;
Tpop4: L←T←stk4, IDISP, :Tpopexit;
Tpop5: L←T←stk5, IDISP, :Tpopexit;
Tpop6: L←T←stk6, IDISP, :Tpopexit;
Tpop7: L←T←stk7, IDISP, :Tpopexit;
Tpopexit: :Fieldra; to permit TASK in Popsub
;-----------------------------------------------------------------
; pushMD dispatch:
; pushes memory value on stack
; The invoking instruction must load MAR and may optionally keep ball 1
; in the air by having a branch pending. That is, entry at 'pushMD' will
; cause control to pass to 'next', while entry at 'pushMDA' will cause
; control to pass to 'nextA'.
;-----------------------------------------------------------------
!3,4,pushMD,pushMDA,StoreB,StoreA;
!17,20,push0,push1,push2,push3,push4,push5,push6,push7,push10,,,,,,,;
pushMD: L←stkp+1, IR←stkp; (IR← causes no branch)
stkp←L, T←0+1, :pushMDa;
pushMDA: L←stkp+1, IR←stkp; (IR← causes no branch)
stkp←L, T←0, :pushMDa;
pushMDa: SINK←DISP, L←T, BUS; dispatch on old stkp value
L←MD, SH=0, TASK, :push0;
;-----------------------------------------------------------------
; Push-T dispatch:
; pushes T on stack
; The invoking instruction may optionally keep ball 1 in the air by having a
; branch pending. That is, entry at 'pushTB' will cause control to pass
; to 'next', while entry at 'pushTA' will cause control to pass to 'nextA'.
;-----------------------------------------------------------------
!1,2,pushT1B,pushT1A; keep ball 1 in air
pushTB: L←stkp+1, BUS, :pushT1B;
pushTA: L←stkp+1, BUS, :pushT1A;
pushT1B: stkp←L, L←T, TASK, :push0;
pushT1A: stkp←L, BUS=0, L←T, TASK, :push0; BUS=0 keeps branch pending
;-----------------------------------------------------------------
; push dispatch:
; strictly vanilla-flavored
; may (but need not) have branch (1) pending if return to 'nextA' is desired
; invoking instruction should specify TASK
;-----------------------------------------------------------------
; Note: the following pre-def occurs here so that dpushof1 can be referenced in push10
!17,20,dpush,,dpush1,dpush2,dpush3,dpush4,dpush5,dpush6,dpush7,dpushof1,dpushof2,,,,,;
push0: stk0←L, :next;
push1: stk1←L, :next;
push2: stk2←L, :next;
push3: stk3←L, :next;
push4: stk4←L, :next;
push5: stk5←L, :next;
push6: stk6←L, :next;
push7: stk7←L, :next;
push10: :dpushof1; honor TASK, stack overflow
;-----------------------------------------------------------------
; Double-word push dispatch:
; picks up alpha from ib, adds it to T, then pushes <result> and
; <result+1>
; entry at 'Dpusha' substitutes L for ib.
; entry at 'Dpushc' and 'DpB' is used by RR 6 logic.
; entry at 'dpush' is used by MUL/DIV/LDIV logic.
; returns to 'nextA' <=> ib = 0 or entry at 'Dpush'
;-----------------------------------------------------------------
!1,2,DpA,DpB;
!1,1,Dpushb; shakes B/A dispatch from RCLK
!5,2,Dpushx,RCLKr; shakes IR←2000 dispatch and
; provides return to RCLK
Dpush: MAR←L←ib+T, :DpB; L: address of low half
Dpusha: SINK←ib, BUS=0;
MAR←L←M+T, :DpA;
DpA: IR←0, :Dpushb; mACSOURCE will produce 0
DpB: IR←2000, :Dpushb; mACSOURCE will produce 1
Dpushb: temp←L, :Dpushx; temp: address of low half
Dpushx: L←MD, TASK, :Dpushc;
Dpushc: taskhole←L; taskhole: low half bits
T←0+1;
L←stkp+T+1;
MAR←temp+1; fetch high half
stkp←L; stkp ← stkp+2
L←taskhole; L: low half bits
SINK←stkp, BUS, :dpush; dispatch on new stkp
dpush: T←MD, :dpush; T: high half bits
dpush1: stk0←L, L←T, TASK, mACSOURCE, :push1; stack cells are S-registers,
dpush2: stk1←L, L←T, TASK, mACSOURCE, :push2; so mACSOURCE does not affect
dpush3: stk2←L, L←T, TASK, mACSOURCE, :push3; addressing.
dpush4: stk3←L, L←T, TASK, mACSOURCE, :push4;
dpush5: stk4←L, L←T, TASK, mACSOURCE, :push5;
dpush6: stk5←L, L←T, TASK, mACSOURCE, :push6;
dpush7: stk6←L, L←T, TASK, mACSOURCE, :push7;
dpushof1: T←sStackOverflow, :KFCr;
dpushof2: T←sStackOverflow, :KFCr;
;-----------------------------------------------------------------
; TOS+T dispatch:
; adds TOS to T, then initiates memory operation on result.
; used as both dispatch table and subroutine - fall-through to 'pushMD'.
; dispatches on old stkp, so MAStkT0 = 1 mod 20B.
;-----------------------------------------------------------------
!17,20,MAStkT,MAStkT0,MAStkT1,MAStkT2,MAStkT3,MAStkT4,MAStkT5,MAStkT6,MAStkT7,,,,,,,;
MAStkT0: MAR←stk0+T, :pushMD;
MAStkT1: MAR←stk1+T, :pushMD;
MAStkT2: MAR←stk2+T, :pushMD;
MAStkT3: MAR←stk3+T, :pushMD;
MAStkT4: MAR←stk4+T, :pushMD;
MAStkT5: MAR←stk5+T, :pushMD;
MAStkT6: MAR←stk6+T, :pushMD;
MAStkT7: MAR←stk7+T, :pushMD;
;-----------------------------------------------------------------
; Common exit used to reset the stack pointer
; the instruction that branches here should have a 'TASK'
; Setstkp must be odd, StkOflw used by PUSH
;-----------------------------------------------------------------
!17,11,Setstkp,,,,,,,,StkOflw;
Setstkp: stkp←L, :next; branch (1) may be pending
StkOflw: :dpushof1; honor TASK, dpushof1 is odd
;-----------------------------------------------------------------
; Stack Underflow Handling
;-----------------------------------------------------------------
StkUf: T←sStackUnderflow, :KFCr; catches dispatch of stkp = -1
;-----------------------------------------------------------------
; Store dispatch:
; pops TOS to MD.
; called from many places.
; dispatches on old stkp, so MDpop0 = 1 mod 20B.
; The invoking instruction must load MAR and may optionally keep ball 1
; in the air by having a branch pending. That is, entry at 'StoreB' will
; cause control to pass to 'next', while entry at 'StoreA' will cause
; control to pass to 'nextA'.
;-----------------------------------------------------------------
!1,2,StoreBa,StoreAa;
!17,20,MDpopuf,MDpop0,MDpop1,MDpop2,MDpop3,MDpop4,MDpop5,MDpop6,MDpop7,,,,,,,;
StoreB: L←stkp-1, BUS;
StoreBa: stkp←L, TASK, :MDpopuf;
StoreA: L←stkp-1, BUS;
StoreAa: stkp←L, BUS=0, TASK, :MDpopuf; keep branch (1) alive
MDpop0: MD←stk0, :next;
MDpop1: MD←stk1, :next;
MDpop2: MD←stk2, :next;
MDpop3: MD←stk3, :next;
MDpop4: MD←stk4, :next;
MDpop5: MD←stk5, :next;
MDpop6: MD←stk6, :next;
MDpop7: MD←stk7, :next;
;-----------------------------------------------------------------
; Double-word pop dispatch:
; picks up alpha from ib, adds it to T, then pops stack into result and
; result+1
; entry at 'Dpopa' substitutes L for ib.
; returns to 'nextA' <=> ib = 0 or entry at 'Dpop'
;-----------------------------------------------------------------
!17,20,dpopuf2,dpopuf1,dpop1,dpop2,dpop3,dpop4,dpop5,dpop6,dpop7,,,,,,,;
!1,1,Dpopb; required by placement of
; MDpopuf only.
Dpop: L←T←ib+T+1;
MDpopuf: IR←0, :Dpopb; Note: MDpopuf is merely a
; convenient label which leads
; to a BUS dispatch on stkp in
; the case that stkp is -1. It
; is used by the Store dispatch
; above.
Dpopa: L←T←M+T+1;
IR←ib, :Dpopb;
Dpopb: MAR←T, temp←L;
dpopuf2: L←stkp-1, BUS;
stkp←L, TASK, :dpopuf2;
dpopuf1: :StkUf; stack underflow, honor TASK
dpop1: MD←stk1, :Dpopx;
dpop2: MD←stk2, :Dpopx;
dpop3: MD←stk3, :Dpopx;
dpop4: MD←stk4, :Dpopx;
dpop5: MD←stk5, :Dpopx;
dpop6: MD←stk6, :Dpopx;
dpop7: MD←stk7, :Dpopx;
Dpopx: SINK←DISP, BUS=0;
MAStkT: MAR←temp-1, :StoreB;
;-----------------------------------------------------------------
; Get operation-specific code from other files
;-----------------------------------------------------------------
#MesacROM.mu;
#MesadROM.mu;