0041 BRK AND NMI ENTRY POINTS TO TIM
0042 -------------------------------
0043 
0044     TIM IS NORMALLY ENTERED WHEN A 'BRK' INSTRUKTION IS
0045         ENCOUNTERED DURING PROGRAM EXECUTION.  AT THAT
0046         TIME CPU REGISTERS ARE OUTPUT:    PC F A X Y SP
0047         AND CONTROL IS GIVEN TO THE KEYBOARD.
0048     USER MAY ENTER TIM BY PROGRAMMED BRK OR INDUCED NMI.  NMI
0049         ENTRIES CAUSE A '#' TO PRECEDE THE '.' IN THE CPU REGISTER
0050         PRINTOUT FORMAT
0051 
0052 NON-BRK INTRO (EXTERNAL DEVICE) INTERRUPT HANDLING
0053 --------------------------------------------------
0054 
0055     A NON-BRK INTRO INTERRUPT CAUSES AN INDIRECT JUMP TO THE ADDRESS
0056         LOCATED AT 'UINT' (HEX FFF8).  THIS LOCATION CAN BE SET
0057         USING THE ALTER CMD, OR LOADED AUTOMATICALLY IN PAPER TAPE
0058         FROM WITH THE LH CMD IF THE USER ASSIGNS HIS INTRO INTERRUPT
0059         VECTOR TO $FFF8 IN THE SOURCE ASSEMBLY PROGRAM.
0060     IF NOT RESET BY THE USER, UINT IS SET TO CAUSE EXTERNAL
0061         DEVICE INTERRUPTS TO ENTER TIM AS NMI'S.  I.E.,
0062         IF A NMI OCOURS WITHOUT AN INDUCED NMI SIGNAL, IT IS
0063         AN EXTERNAL DEVICE INTERRUPT.
0064 
0065 SETTING AND RESETTING PROGRAM BREAKPOINTS
0066 -----------------------------------------
0067 
0068     BREAKPOINTS ARE SET AND RESET USING THE MEMORY DISPLAY
0069         AND ALTER COMMANDS.  BRK HAS A '00' OPERATION CODE.
0070     TO SET A BREAKPOINT SIMPLY DISPLAY THE MEMORY LOCATION
0071         (FIRST INSTRUCTION BYTE) AT WHICH THE BREAKPOINT IS
0072         TO BE PLACED THEN ALTER THE LOCATION TO '00'.  THERE IS
0073         NO LIMIT TO THE NUMBER OF BREAKPOINTS THAT CAN BE
0074         ACTIVE AT ONE TIME.
0075     TO RESET A BREAKPOINT, RESTORE THE ALTERED MEMORY LOCATION
0076         TO ITS ORIGINAL VALUE.
0077     WHEN AND IF A BREAKPOINT IS ENCOUNTERED DURING EXECUTION,
0078         THE BREAKPOINT DATA PRECEDEC BY AN ':' IS DISPLAYED.
0079         THE PROGRAM COUNTER VALUE DISPLAYED IS THE BRK
0080         INSTRUCTION LOCATION + 1.

0140   7000 85 F9       NMINT  STA ACC
0141   7002 A9 23              LDA #'#'           ; SET A=# TO INDICATE NMINT ENTRY
0142   7004 D0 55              BNE B3            ; JMP B3
0143   7006             ;

0190   7050             ;
0191   7050 58                 CLI               ; ENABLE INTS
0192   7051 00                 BRK               ; ENTER TIM BY BRK
0193   7052   

          ;
0194   7052 85 F9       INTRQ  STA ACC           ; SAVE ACC
0195   7054 68                 PLA               ; FLAGS TO A
0196   7055 48                 PHA               ; RESTORE STACK STATUS
0197   7056 29 10              AND #$10          ; TEST BRK FLAG
0198   7058 F0 27              BEQ BX            ; USER INTERRUPT
0199   705A             ;
0200   705A 0A                 ASL A             ; SET A=SPACE (10 X 2 = 2C)
0201   705B 85 FE       B3     STA TMPC          ; SAVE INT TYPE FLAG
0202   705D D8                 CLD               ; CLEAR DECIMAL MODE
0203   705E 4A                 LSR A             ; # IS ODD, SPACE IS EVEN
0204   705F                                      ; SET CY FOR PC BRK CORRECTION
0205   705F             ;
0206   705F 86 FA              STX XR            ; SAVE X
0207   7061 84 FB              STY YR            ; Y
0208   7063 68                 PLA
0209   7064 85 F8              STA FLGS          ; FLAGS
0210   7066 68                 PLA
0211   7067 69 FF              ADC #$FF          ; CY SET TO PC-1 FOR BRK
0212   7069 85 F6              STA PCL
0213   706B 68                 PLA
0214   706C 69 FF              ADC #$FF
0215   706E 85 F7              STA PCH
0216   7070 BA                 TSX
0217   7071 86 FC              STX SP            ; SAVE ORIG SP
0218   7073             ;
0219   7073 20 8A 72    B5     JSR CRLF
0220   7076 A6 FE              LDX TMPC
0221   7078             ;
0222   7078 A9 2A              LDA #'*'
0223   707A 20 C0 72           JSR WRTWO
0224   707D A9 52              LDA #'R'           ; SET FOR R DISPLAY TO PERMIT
0225   707F D0 16              BNE S0            ;   IMMEDIATE ALTER FOLLOWING BREAKPOINT.
0226   7081             ;
0227   7081 A5 F9       BX     LDA ACC
0228   7083 6C F8 FF           JMP (UINT)        ; CONTROL TO USER INTRO SERVICE ROUTINE