Sample session

 *  7052 B0 00 FF 00 FF
.M  0200 00 00 00 00 00 00 00 00
.:  0200 33 44 55
.M  0200 33 44 55 00 00 00 00 00
.R  7052 B0 00 FF 00 FF
.:  3455 55 55 55 55 55
.R  3455 55 55 55 55 55
.M  00F6 55 34 55 55 55 55 55 02
.M  7000 85 F9 A9 23 D0 55 A9 16
.:  7000 77?
.?
.

The ‘:’ command reacts different upon previous actions:

• if the previous command was M, the current address types in with M is printed and bytes can be typed in that will be placed at the current PC. The current address is incremented and the next byte can be entered, till maximum 8 are entered 85
• if the previous command was R the program counter has to be typed and the 5 registers PS A X Y Z (or less by pressing ENTER).
• after a ‘:’ command, the next ‘:’ will behave the same as following the M command

Note the current address and the Program Counter are not the same. The GO command requires the Program Counter to be set to the desired address.

0282   70E0             ;
0283   70E0             ;  READ AND STORE BYTE.  NO STORE IF SPACE OR RCNT=0.
0284   70E0             ;
0285   70E0 20 B3 73    BYTE   JSR RDOB          ; CHAR IN A, CY=0 IF SP
0286   70E3 90 10              BCC BY3           ; SPACE
0287   70E5             ;
0288   70E5 A2 00              LDX #0            ; STORE BYTE
0289   70E7 81 EE              STA (TMP0,X)
0290   70E9             ;
0291   70E9 C1 EE              CMP (TMP0,X)      ; TEST FOR VALID WRITE (RAM)
0292   70EB F0 05              BEQ BY2
0293   70ED 68                 PLA               ; ERR, CLEAR JSR ADR IN STACK
0294   70EE 68                 PLA
0295   70EF 4C BA 70           JMP ERROPR
0296   70F2             ;
0297   70F2 20 7C 72    BY2    JSR CADD          ; INCR CKSUM
0298   70F5 20 97 73    BY3    JSR INCTMP        ; GO INCR TMPO ADR
0299   70F8 C6 FE              DEC RCNT
0300   70FA 60                 RTS

BYTE

What is happening here?

• Read a byte (two hex characters) (285)
• if space skip writing databyte (286, 289)
• store as binary in current address and increment current address (289)
• if databyte read back is not equal databyte then error out of caller also (291-295)
• add to checksum (checksum is part of L command) (297)
• increment address to store into (298)
• decrement number of bytes to write (299)

0272   70D0 A5 EE       PUTP   LDA TMP0          ; MOVE TMP0 TO PCH,PCL
0273   70D2 85 F6              STA PCL
0274   70D4 A5 EF              LDA TMP0+1
0275   70D6 85 F7              STA PCH
0276   70D8 60                 RTS

0302   70FB A9 F8       SETR   LDA #FLGS         ; SET TO ACCESS REGS
0303   70FD 85 EE              STA TMP0
0304   70FF A9 00              LDA #0
0305   7101 85 EF              STA TMP0+1
0306   7103 A9 05              LDA #5
0307   7105 60                 RTS

PUTP
Move current address in TMP0 to Program Counter PCL

SETR

• The address of the saved registers is loaded in TMP0, TMP0+1
• A is laoded with 5, to let DSPLYM show the registers SP A X Y Z

0349   713A             ;  ALTER LAST DISPLAYED ITEM (ADR IN TMPC)
0350   713A             ;
0351   713A C6 E9       ALTER  DEC PREVC         ; R INDEX = 1
0352   713C D0 0D              BNE A3
0353   713E             ;
0354   713E 20 A4 73           JSR RDOA          ; CY=0 IF SP
0355   7141 90 03              BCC A2            ; SPACE
0356   7143 20 D0 70           JSR PUTP          ; ALTER PC
0357   7146 20 FB 70    A2     JSR SETR          ; ALTER R*S
0358   7149 D0 05              BNE A4            ; JMP A4 (SETR RETURNS ACC = 5)
0359   714B 20 9A 72    A3     JSR WROA          ; ALTER M, TYPE ADR
0360   714E A9 08              LDA #8            ; SET CNT=8
0361   7150             ;
0362   7150 85 FE       A4     STA RCNT
0363   7152 20 77 73    A5     JSR SPACE         ; PRESERVES Y
0364   7155 20 E0 70           JSR BYTE
0365   7158 D0 F8              BNE A5
0366   715A F0 D8       A9     BEQ BEQS1

0345   7134 4C 86 70    BEQS1  JMP START

What is happening here?

• decrement previous command index(set in START) :=1 R=2 M=3 (351-352)
• if > 0 then M command, also resets R command mode (358)
• else previous was R command: read address and put in Program counter (354-358, 362)
• set current address to registers (FLGS) and 5 bytes to write (357)
• M command: show address, 8 bytes to write (360-361
• loop bytes to write
• print space (363)
• read and store byte (if not space) (364)
• if error entering byte then error out via BYTE
• until all bytes to write are done(365)
• back to START for next command 366, 345)