Execution commands of uCsim

g [start [stop]]

 Go, start execution. Parameters are optional. First parameter specifies start address of the execution. By default execution starts at address specified by actual value of the PC. This can be overridden by first parameter. If second parameter is specified it places a dynamic breakpoint at specified address which stops the execution. If stop address is not given the simulator stops if it reaches a breakpoint, or the CPU accepts an interrupt and stopit option is TRUE, or fatal error occures or stop command is used. Note that first instruction is executed without effect of breakpoints. It means that if there is a breakpoint at start address then it will not be hit. 
$ s51 remoansi.hex
ucsim 0.2.24, Copyright (C) 1997 Daniel Drotos, Talker Bt.
ucsim comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
55755 bytes read from remoansi.hex
> b 0x187
> sopt stopit y
> g
Simulation started, PC=0x000000
Stop at 000187: (4) Breakpoint
F 000187
>
After execution is started the Simulaton started message appears with value of PC where the execution started and the simulator is ready to accept other commands while the simulation is running in background.

stop

 This command stops the simulation, it freezes the CPU and all the peripherials. 
$ s51 remoansi.hex
ucsim 0.2.24, Copyright (C) 1997 Daniel Drotos, Talker Bt.
ucsim comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
58659 bytes read from remoansi.hex
> g
Simulation started
> dr
000000 00 01 00 14 00 00 5a 47 ......ZG
000000 00 .  ACC= 0x47  71 G  B= 0x01   DPTR= 0x001c @DPTR= 0x47  71 G
000001 01 .  PSW= 0x00 CY=0 AC=0 OV=0 P=0
   006f02 90 00 1e MOV   DPTR,#001e
> stop
   006ac5 24 a5    ADD   A,#a5
>
Simulated program is executed in background and the simulator accepts commands. If it stopped by the stop command the instruction pointed by PC is dissassembled, see the dis command for description of disassembled form.

[Repeatable] s [step]

 Step command. It executes one instruction without effect of breakpoints. Optional parameter can specify number of requested steps. 
$ s51 remoansi.hex
ucsim 0.2.12, Copyright (C) 1997 Daniel Drotos, Talker Bt.
ucsim comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
58659 bytes read from remoansi.hex
> s
000000 00 00 00 00 00 00 00 00 ........
000000 00 .  ACC= 0x00   0 .  B= 0x00   DPTR= 0x0000 @DPTR= 0x00   0 .
000000 00 .  PSW= 0x00 CY=0 AC=0 OV=0 P=0
   000160 c2 90    CLR   P1.0
> s 2
000000 00 00 00 00 00 00 00 00 ........
000000 00 .  ACC= 0x00   0 .  B= 0x00   DPTR= 0x0000 @DPTR= 0x00   0 .
000000 00 .  PSW= 0x00 CY=0 AC=0 OV=0 P=0
   000162 c2 97    CLR   P1.7
000000 00 00 00 00 00 00 00 00 ........
000000 00 .  ACC= 0x00   0 .  B= 0x00   DPTR= 0x0000 @DPTR= 0x00   0 .
000000 00 .  PSW= 0x00 CY=0 AC=0 OV=0 P=0
   000164 d2 b5    SETB  P3.5
>
After execution of actual instruction pointed by PC the step command executes dr command.

[Repeatable] n [step]

 Execute until next instruction is reached. This command is similar to step command described above but if actual instruction to execute is a subroutine call the next command places a dynamic breakpoint after the call instruction and starts to execute the subroutine. If the subroutine is infinite the breakpoint set by next will never reached. It can be a dangerous situation because the executeion started by the next command can not be stopped interactively. But it can be stopped by other breakpoints. 
$ s51 remoansi.hex
ucsim 0.2.12, Copyright (C) 1997 Daniel Drotos, Talker Bt.
ucsim comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
58659 bytes read from remoansi.hex
> g 0 0x172
4
   000172 79 04    MOV   R1,#04
> dis 0x172 0 5
   000170 7f 00    MOV   R7,#00
   000172 79 04    MOV   R1,#04
   000174 12 0d b8 LCALL 0db8
   000177 0f       INC   R7
   000178 d9 fa    DJNZ  R1,0174
   00017a 75 0b 00 MOV   0b,#00
> n 3
000000 00 04 00 00 00 00 00 00 ........
000000 00 .  ACC= 0x00   0 .  B= 0x00   DPTR= 0x0000 @DPTR= 0x00   0 .
000004 00 .  PSW= 0x00 CY=0 AC=0 OV=0 P=0
   000174 12 0d b8 LCALL 0db8
000000 00 04 00 00 00 00 00 00 ........
000000 00 .  ACC= 0x00   0 .  B= 0x00   DPTR= 0x0167 @DPTR= 0x00   0 .
000004 00 .  PSW= 0x00 CY=0 AC=0 OV=0 P=0
   000177 0f       INC   R7
000000 00 04 00 00 00 00 00 01 ........
000000 00 .  ACC= 0x00   0 .  B= 0x00   DPTR= 0x0167 @DPTR= 0x00   0 .
000004 00 .  PSW= 0x00 CY=0 AC=0 OV=0 P=0
   000178 d9 fa    DJNZ  R1,0174
>

pc [address]

 Using this command without any parameter it simply dumps out instruction pointed by the PC. Specify address if you want to set the PC. 
$ s51
S51 0.1.5, Copyright (C) 1997 Daniel Drotos, Talker Bt.
S51 comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.
> pc
 * 000000 ff       MOV   R7,A
> pc 123
 * 00007b ff       MOV   R7,A
> sopt debug t  
> pc 32
Warning: maybe not instruction at 000020
 * 000020 ff       MOV   R7,A
>

run

 This command starts the execution of the simulated program.