{File name: CoreInitial.mc
Description: 2MB Purcell Core of the initial microcode booting sequence,
Last Edited: Purcell 2-Mar-84 5:16:02 remove Bank ← 4
Last Edited: Purcell 15-Feb-84 1:29:59 recognize 4mb
Last Edited: Purcell February 6, 1984 12:29 PM MCtl ← 8002h or xx
Last Edited: Purcell January 19, 1984 7:25 PM Mesa ignore xtra mem
Last Edited: Purcell January 16, 1984 6:35 PM test for 4MB
Last Edited: Purcell January 4, 1984 6:46 PM Bank ← 4{21 bit real mem}
Last Edited: Purcell December 30, 1983 11:17 AM MCtl ← 2.
Last Edited: Purcell December 29, 1983 5:00 PM 3-8MB mem.
Last Edited: Purcell December 27, 1983 9:14 PM 2MB mem.
Last Edited: Neely, April 2, 1982 6:28 PM @ TridentInit elim use of U0400.
Last Edited: Neely, December 11, 1981 9:59 AM Eliminated mapZap subr.
Last Edited: Neely, November 13, 1981 3:47 PM Added Trident Switch.
Last Edited: Jarvis, March 21, 1981 8:39 AM
Created: Jarvis, November 12, 1980}

Reserve[ProtectStart, ProtectFence], Reserve[0FE0, 0FFF];{save room for boot kernel}

{IO page offsets}
Set[DPYCtlWord, 0EC]; {8000=> turn display off}

{Set[realBankCnt, 0C];{1.5}
Set[realBankCnt, 10];{2.0}
Set[realBankCnt, 0A0];
Set[realBankCnt, 08F];
}
Set[realBankCnt, 090];

Set[realBankCntM1, Sub[realBankCnt, 1]];
SetTask[0], StartAddress[go];

go:{MCtl ←} rB{← 8002h} ← RRot1 5, CANCELBR[$, 0F],c1;
IOPCtl← 0,c2;
IfGreater[Config,1,SkipTo[TridentInit],];

KCtl← 0,c3; {SAx000}
SkipTo[NoTridentInit];

TridentInit!
RCnt ← 0F,c3; {Trident}
KCtl ← RCnt LRot12,c1; {Trident}
acR ← 4,c2; {Trident}
KCmd ← acR LRot8,c3; {Trident}

NoTridentInit!

DCtl← 3,c1; {display black, enable task}
PCtl← 0,c2;
EICtl← 0,c3;
EOCtl← 0,c1;
acR← 40,c2;
acR← acR LRot8,c3;
IOPageLow← acR,c1;
MCtl{← 8002h} ← rB, rB ← 4{21 bit real mem},c2;
Noop{Bank ← rB}, {GOTO[mapInit],}c3;

{*}acR← uDiagnostic,c1;
{*}[]← acR{uDiagnostic} - 1, ZeroBr,c2;
Q ← 55{Mesa}, BRANCH[qMBoot, qLBoot],c3;

qLBoot:[]← Q xor uLispBootMsg, ZeroBr,c1;
Noop, BRANCH[rLBoot, rMBoot],c2;
rMBoot:uDiagnostic← 0, GOTO[qMBoot],c3;
rLBoot:Noop,c3;

qMBoot:
rB ← 0AA{Lisp},c1;
uLispBootMsg ← rB,c2;
Noop, GOTO[mapInit],c3;

{map initialization goes on during this interval}

mapRet:
{clear all but the first two pages of bank 0}
acR← 0,c2;
passTraps← acR,c3;
rD← 2,c1;
rD← rD LRot8,c2;
rDrh← 0,c3;

clear:MAR← [rDrh, rD+0],c1;
MDR← acR, rD← rD+1, ZeroBr,c2;
BRANCH[clear, $],c3;

Noop,c1;
acR← 0FF+1,c2;
uBootStart← acR, GOTO[OnceOnlyInit],{%}c3;

trapIt:Noop, GOTO[trapIt],c*;

{OnceOnlyInit transfers control to DoneOnceOnlyInit. DoneOnceOnlyInit lives in the device specific initial microcode. When that finishes, control passes to exitToEmulator.}

exitToEmulator:

{swap entries for IO page and 0}
mapIO:rE← 0,c1;
rErh← 1,c2;
rB← virtualIOPage, L0← 0F,c3;
rBrh← 1, CALL[memSwap2],c1;

Noop,c1, at[0F, 10, subrRet];
Noop,c2;

{make sure the display is off when the germ starts}
DPYOff:acR← RShift1 0, SE← 1,c3; {acR← 8000}
rE← IOPageLow,c1; {IOPage real address}
rB← 0,c2;
rBrh← 0,c3;
MAR← [rErh, DPYCtlWord+0],c1;
MDR← acR,c2;


enableIOP:Noop,c3;
MAR← [rBrh, 0+0],c1;
MDR← 0FF,c2;
Noop,c3;
MAR← [rBrh, 0+1],c1;
MDR← uBootStart, CANCELBR[$, 0],c2;
IOPCtl← IOPInMode, GOTOABS[IdleLoc],c3;

{subroutines and end matter}

{Map initialization -- Sets up map and leaves next available page in topPage. Start looking for pages before 768K, i.e., below bank 0C. Does not map any pages in bank 0.

Beware -- clobbers the first word of each page in bank 0 even though you don’t mean it!!!!!!!!!!!!!!!!!!!!!!!!

Write page number in the first word of each page. Go through memory top down to give lower addresses precedence

Register usage
acRpage number
rBmemory address register
rCtemporary
rDtemporary
rEnext available page}

mapInit:rBrh← realBankCnt{C}, {start in bank 90{B}}c1;
rB{0}← 0,c2; {address within bank}
passTraps← acR xor ~acR,c3; {catch faults}
acR← realBankCnt,{start in bank 90{0F}{B}}c1;
acR← acR LRot8, GOTO[mark1],c2; {page counter}

{mark the first word of each page with its page number}
markPages:MAR← [rBrh, rB+0],c1;
MDR← acR, ZeroBr,c2;
mark1:acR← acR-1, {NegBr,} BRANCH[$, mapBuild1],c3; {written all pages?}
rC← 0FF+1, {BRANCH[$, mapBuild],}c1;
rC← rB-rC, CarryBr,c2;
rB← rC, BRANCH[$, markPages],c3;
rB← rBrh,c1;
rB← rB-1,c2;
rBrh← rB LRot0,c3;
rB← rC,c1;
Noop,c2;
GOTO[markPages],c3;

mapBuild:Noop,c2;
Noop,c3;
mapBuild1:rBrh← 1,c1;
rC← rCrh← 1,c2;
rB← 0,c3;

{make all pages vacant}
MAR← [rBrh, rB+0],c1;
MDR← vacant,c2;
acR← mapPages,c3;
acR← acR LRot8, L0← 0A,c1;
acR← acR-1, CALL[BLT3],c2;

Noop,c1, at[0A, 10, subrRet];
rE← 0, {start at virtual 0}c2;
rErh← 1,c3; {map in bank 1}
rBrh←1,c1; {so is the IO page}
rB← IOPageLow,c2;
acR← rB LRot8,c3; {start mapping pages . . . }
acR← acR+0FF+1,c1; {IO page is in bank 1}

{page should have its own page number in the first location}
mapLoop2:Noop,c2;
mapLoop:Noop,c3;
mapLoop1:MAR← [rBrh, rB+0], CANCELBR[$,1],c1;
Noop,c2;
rC← MD, {double error bit error possible here}c3;
Noop,c1;
[]← rC xor acR, ZeroBr,c2;
acR← acR+1, BRANCH[nextReal, $],c3;

{map this page in}
topPage← rB,c1;
Noop,c2;
Noop,c3;
rB← rB or rBrh,c1; {map entry for this page}
rC← rB,c2;
rB← topPage,c3;
MAR← [rErh, rE+0],c1;
MDR← rC or present,c2;
rE← rE+1,c3;
nextReal:rC← 0FF+1,c1;
rB← rB+rC, CarryBr,c2;
Q← rBrh, BRANCH[$, nextBank],c3;
Noop, GOTO[mapLoop2],c1;

nextBank:rC← Q+1, PgCarryBr, c1;
rBrh← rC LRot0, BRANCH[$, clearMem3],c2;
Noop,c3;

Q← uDiagnostic,c1;
[]← Q{uDiagnostic} - 1, ZeroBr{uD=1},c2;
[]← rC xor 0C, ZeroBr, BRANCH[$, mapLoop1],c3;
Noop, BRANCH[mapLoop2, clearMem2],c1;

{clear all mapped pages}
clearMem2:Noop,c2;
clearMem3:Noop,c3;
clearMem:topPage← rE,c1; {save away}
rE← 0,c2; {word offset}
rD← 0,c3; {source of zero}
passTraps← rD, {die on double bit errors}c1;
Noop,c2;
Noop,c3;

clearLoop:MAR← [rErh, rE+0],c1; {read the map}
rC← 0,c2;
acR← MD,c3;

rB← acR {and 0F},c1;
rBrh← rB LRot0,c2;
rB← acR and ~0FF,c3;

{write into every word of the page}
clearPage:MAR← [rBrh, rC+0],c1;
MDR← rD, rC← rC+1, PgCarryBr,c2;
acR← topPage, BRANCH[clearPage, $],c3;

rE← rE+1,c1;
[]← rE xor acR, ZeroBr,c2; {compare to topPage}
BRANCH[clearLoop, $],c3;

GOTO[mapRet],c1;

{trap catcher, gets here with rC← RRot1 ErrnIBnStkp}
error:Xbus← rC LRot0, XwdDisp,c2, at[ErrorHandlerLoc];
DISP2[errorType],c3;

GOTO[death], {control store parity error}c1, at[0, 4, errorType];
Xbus← MStatus, XLDisp, GOTO[memFault],c1, at[1, 4, errorType];
GOTO[death], {stack error}c1, at[2, 4, errorType];
GOTO[death], {instruction buffer empty}c1, at[3, 4, errorType];
death:GOTO[death],c*;

memFault:BRANCH[death, $, 1],c2; {map out of bound?}
GOTO[nextReal],c3; {no, double bit error}

{block transfer, takes count in acR, from in rB, and to in rC, returns first word past from block in rE}
BLT2:Noop,c2;
BLT3:Noop,c3;
BLT:MAR← [rBrh, rB+0],c1;
[]← acR, ZeroBr,c2;
rE← MD, BRANCH[$, endBLT],c3;
MAR← [rCrh, rC+0],c1;
MDR← rE,c2;
acR← acR-1,c3;
rB← rB+1,c1;
rC← rC+1,c2;
GOTO[BLT],c3;
endBLT:Noop,c1;
endBLT1:pRet0,c2;
endBLT2:RET[subrRet],c3;

{******* Not used anymore
{takes count in acR, virtual page number in rE, and map entry in rC. Beware, rErh better have a 1 !!!!}
mapZap3:Noop,c3;
mapZap:MAR← [rErh, rE+0],c1;
MDR← rC or present,c2; {referenced and present}
rC← rC+0FF+1,c3;
rE← rE+1,c1;
acR← acR-1, ZeroBr,c2;
BRANCH[mapZap, $],c3;
Noop,c1;
endMisc1:pRet0,c2;
endMisc2:RET[miscRet],c3;
*********}
{swaps two locations in memory, takes address in rE and rB, clobbers acR}
memSwap2:Noop,c2;
memSwap3:Noop,c3;
memSwap:MAR← [rErh, rE+0],c1;
Noop,c2;
acR← MD,c3;
MAR← [rBrh, rB+0],c1;
MDR← acR,c2;
acR← MD,c3;
MAR← [rErh, rE+0],c1;
MDR← acR, pRet0,c2;
RET[subrRet],c3;