Execution commands of µCsim

r,run,go [start [stop]]

This command starts the execution of the simulated program.

Parameters are optional. First parameter specifies the start address for execution. By default, execution starts at the address specified by the PC's actual value. This can be overridden by the first parameter.

If second parameter is specified, it places a dynamic breakpoint at the specified address, which stops the execution at that address. If a stop address is not given the simulator stops if it reaches a breakpoint that was previously set, or the CPU accepts an interrupt and stopit option is TRUE, or fatal error occurs or stop command is used on an other console, or ENTER key is pressed on the console where the run command was issued.

When program execution is started, the console becomes frozen; it is not possible to give commands on this console to the simulator while execution is running. If it is needed to control the simulator during program execution then more consoles can be used. See using multiple consoles for more information. Meanwhile, simulation can be stopped by pressing the ENTER key (or type in a command and ENTER) on the frozen console (where the run command was issued).

If run command is used in a script (standard input or file parameter for -C option), the execution of the script is always suspended on the run command. The script resumes after execution stops.

However, it is possible to start the simulation in the background by setting the sim_run variable to a logical TRUE (i.e. non-zero) value, like:

$ ucsim_51
uCsim 0.9.10, Copyright (C) 1997 Daniel Drotos.
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.
0> load "remo.hex"
Loading from remo.hex
55755 words read from remo.hex
0> sim_run=1
1
0> info reg
     R0 R1 R2 R3 R4 R5 R6 R7
     18 00 46 83 00 00 00 00
@R0 c2 .  ACC= 0x00   0 .  B= 0x00
@R1 18 .  PSW= 0x00 CY=0 AC=0 OV=0 P=0
SP 0x2e -> 77 f3 79 84 c9 28 24 e4
   DPTR= 0x000e @DPTR= 0x00   0 .
0x7057    ff       MOV    R7,A
0>

Note that the first instruction is executed without the effect of breakpoints and simulation will be started afterwards. It means that if there is a breakpoint at start address then it will not be hit. See following example:

$ ucsim_51
uCsim 0.9.10, Copyright (C) 1997 Daniel Drotos.
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.
0> b 0x10
Breakpoint 1 at 0x000010 (cond="")
0x0010 F  ff       MOV    R7,A
0> b 0x20
Breakpoint 2 at 0x000020 (cond="")
0x0020 F  ff       MOV    R7,A
0> run 0x10
Simulation started, PC=0x000010

Stop at 0x000020: (104) Breakpoint
     R0 R1 R2 R3 R4 R5 R6 R7
     41 58 fc c9 8b bc 95 00
@R0 76 v  ACC= 0x00   0 .  B= 0x00
@R1 73 s  PSW= 0x00 CY=0 AC=0 OV=0 P=0
SP 0x07 -> 00 95 bc 8b c9 fc 58 41
   DPTR= 0x0000 @DPTR= 0x83 131 .
0x0020 F  ff       MOV    R7,A
F 0x000020
Simulated 192 ticks (1.736e-05 sec)
Host usage: 0.000004 sec, rate=4.283399
0>

emulation

It starts simulation in so called "emulation" mode. In this mode µCsim does not handle any user input, which means that all consoles will be frozen and inputs for UARTs will be skipped.

In emulation mode the simulation cannot be stopped by any user interaction. Breakpoints or the simulator interface must be used to stop the simulation.

stop

This command stops the simulation; it freezes the CPU and all the peripherals.

$ ucsim_51
uCsim 0.9.10, Copyright (C) 1997 Daniel Drotos.
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.
0> load "remo.hex"
Loading from remo.hex
55755 words read from remo.hex
0> sim_run=1
1
0> info reg
     R0 R1 R2 R3 R4 R5 R6 R7
     18 00 46 83 00 00 00 00
@R0 c2 .  ACC= 0x00   0 .  B= 0x00
@R1 18 .  PSW= 0x00 CY=0 AC=0 OV=0 P=0
SP 0x2e -> 77 f3 79 84 c9 28 24 e4
   DPTR= 0x000e @DPTR= 0x00   0 .
0x7057    ff       MOV    R7,A
0> info reg
     R0 R1 R2 R3 R4 R5 R6 R7
     18 01 00 d2 00 01 00 31
@R0 67 g  ACC= 0x31  49 1  B= 0x00
@R1 01 .  PSW= 0x01 CY=0 AC=0 OV=0 P=1
SP 0x28 -> 25 d7 29 81 02 2d 06 27
   DPTR= 0x00d2 @DPTR= 0x31  49 1
0x367d    20 0c 02 JB     0x0c,0x3682
0> stop
0x93c7    90 09 30 MOV    DPTR,#0x0930
0>

After using the stop command, the instruction pointed by PC is disassembled, see the dis command for description of disassembled form.

s,step [steps]

The Step command. It executes one instruction without the effect of breakpoints.

The optional parameter can be used to specify the number of instructions to execute. Note that breakpoints will stop the execution after the first instruction.

$ ucsim_51
uCsim 0.9.10, Copyright (C) 1997 Daniel Drotos.
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.
0> load "remo.hex"
Loading from remo.hex
55755 words read from remo.hex
0> step

Stop at 0x000160: (109) stepped 24 ticks
     R0 R1 R2 R3 R4 R5 R6 R7
     41 58 fc c9 8b bc 95 6b
@R0 76 v  ACC= 0x00   0 .  B= 0x00
@R1 73 s  PSW= 0x00 CY=0 AC=0 OV=0 P=0
SP 0x07 -> 6b 95 bc 8b c9 fc 58 41
   DPTR= 0x0000 @DPTR= 0x83 131 .
0x0160    c2 90    CLR    0x900x90 <P1>.0
F 0x000160
0> step 1 s

Stop at 0x004366: (104) Breakpoint
     R0 R1 R2 R3 R4 R5 R6 R7
     0c 01 0b 8f 00 86 0c 00
@R0 00 .  ACC= 0x00   0 .  B= 0x00
@R1 01 .  PSW= 0xc0 CY=1 AC=1 OV=0 P=0
SP 0x26 -> 2a ae 02 2d 3e 37 bc 00
   DPTR= 0x000e @DPTR= 0x00   0 .
0x4366    90 00 0a MOV    DPTR,#0x000a
F 0x004366
Simulated 11059212 ticks (1.000e+00 sec)
Host usage: 0.112313 sec, rate=8.903696
0> step 100 vclk

Stop at 0x004396: (104) Breakpoint
     R0 R1 R2 R3 R4 R5 R6 R7
     0c 01 0b 8f 00 86 0c 00
@R0 00 .  ACC= 0x00   0 .  B= 0x00
@R1 01 .  PSW= 0xc0 CY=1 AC=1 OV=0 P=0
SP 0x26 -> 2a ae 02 2d 3e 37 bc 00
   DPTR= 0x000b @DPTR= 0x00   0 .
0x4396    ff       MOV    R7,A
F 0x004396
Simulated 672 ticks (6.076e-05 sec)
Host usage: 0.000012 sec, rate=5.097244
0>

After execution of the actual instruction pointed by PC (or all instructions specified by the optional parameter) the step command dumps out the register set.

The number of steps can be specified in different units. If no unit is appended to step number then it will be interpreted as the number of instruction. Other know units are:

s, sec: Simulated execution time in seconds.
ms, msec: Simulated execution time in milliseconds.
us, usec: Simulated execution time in microseconds.
ns, nsec: Simulated execution time in nanoseconds.
vclk: Number of virtual clock counts.
fclk, fetch: Number of fetches.
rclk, read: Number of memory read operations.
wclk, write: Number of memory write operations.

n,next

It executes until the next instruction is reached. This command is similar to the step command described above but if the 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 be reached. This can be a dangerous situation because the execution started by the next command cannot be stopped interactively. But it can be stopped by other breakpoints.

$ ucsim_51
uCsim 0.9.10, Copyright (C) 1997 Daniel Drotos.
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.
0> load "remo.hex"
Loading from remo.hex
55755 words read from remo.hex
0> run 0 0x172
Simulation started, PC=0x000000

Stop at 0x000172: (104) Breakpoint
     R0 R1 R2 R3 R4 R5 R6 R7
     41 58 fc c9 8b bc 00 00
@R0 76 v  ACC= 0x00   0 .  B= 0x00
@R1 73 s  PSW= 0x00 CY=0 AC=0 OV=0 P=0
SP 0x22 -> 1d 84 43 31 94 d0 c9 03
   DPTR= 0x0000 @DPTR= 0x83 131 .
0x0172    79 04    MOV    R1,#0x04
F 0x000172
Simulated 144 ticks (1.302e-05 sec)
Host usage: 0.000014 sec, rate=0.925650
0> disass 0x172 0 5
Removed command, use "dc" instead
0> next

Stop at 0x000174: (109) stepped 12 ticks
     R0 R1 R2 R3 R4 R5 R6 R7
     41 04 fc c9 8b bc 00 00
@R0 76 v  ACC= 0x00   0 .  B= 0x00
@R1 8b .  PSW= 0x00 CY=0 AC=0 OV=0 P=0
SP 0x22 -> 1d 84 43 31 94 d0 c9 03
   DPTR= 0x0000 @DPTR= 0x83 131 .
0x0174    12 09 f9 LCALL  0x09f9
F 0x000174
0> n

Stop at 0x000177: (104) Breakpoint
     R0 R1 R2 R3 R4 R5 R6 R7
     41 04 fc c9 8b bc 00 00
@R0 76 v  ACC= 0x00   0 .  B= 0x00
@R1 8b .  PSW= 0x00 CY=0 AC=0 OV=0 P=0
SP 0x22 -> 1d 84 43 31 94 d0 c9 03
   DPTR= 0x0149 @DPTR= 0x00   0 .
0x0177    0f       INC    R7
F 0x000177
Simulated 492 ticks (4.449e-05 sec)
Host usage: 0.000015 sec, rate=2.961834
0>

pc [address]

Using this command without any parameter it simply dumps out the instruction pointed by the PC. Specify the address if you want to set the PC.

$ ucsim_51
uCsim 0.9.10, Copyright (C) 1997 Daniel Drotos.
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.
0> pc
0x0000    ff       MOV    R7,A
0> pc 123
0x007b    ff       MOV    R7,A
0> info reg
     R0 R1 R2 R3 R4 R5 R6 R7
     41 58 fc c9 8b bc 95 6b
@R0 76 v  ACC= 0x00   0 .  B= 0x00
@R1 73 s  PSW= 0x00 CY=0 AC=0 OV=0 P=0
SP 0x07 -> 6b 95 bc 8b c9 fc 58 41
   DPTR= 0x0000 @DPTR= 0x83 131 .
0x007b    ff       MOV    R7,A
0>

history

The History command can be used to inspect and manipulate the history of executed instructions. It accepts the following subcommands:

history
history information
history list
history clear

history

This command (without a subcommand) prints out the last 10 elements of the command history in disassembled form.

$ ucsim_51
uCsim 0.9.10, Copyright (C) 1997 Daniel Drotos.
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.
0> load "remo.hex"
Loading from remo.hex
55755 words read from remo.hex
0> step 10

Stop at 0x000174: (109) stepped 156 ticks
     R0 R1 R2 R3 R4 R5 R6 R7
     41 04 fc c9 8b bc 00 00
@R0 76 v  ACC= 0x00   0 .  B= 0x00
@R1 8b .  PSW= 0x00 CY=0 AC=0 OV=0 P=0
SP 0x22 -> 1d 84 43 31 94 d0 c9 03
   DPTR= 0x0000 @DPTR= 0x83 131 .
0x0174    12 09 f9 LCALL  0x09f9
F 0x000174
Simulated 156 ticks (1.411e-05 sec)
Host usage: 0.000015 sec, rate=0.939118
0> history
0x0000    02 01 60 LJMP   0x0160
0x0160    c2 90    CLR    0x900x90 <P1>.0
0x0162    c2 97    CLR    0x970x90 <P1>.7
0x0164    d2 b5    SETB   0xb50xb0 <P3>.5
0x0166    d2 b4    SETB   0xb40xb0 <P3>.4
0x0168    75 81 22 MOV    0x81 <SP>,#0x22
0x016b    75 d0 00 MOV    0xd0 <PSW>,#0x00
0x016e    7e 00    MOV    R6,#0x00
0x0170    7f 00    MOV    R7,#0x00
0x0172    79 04    MOV    R1,#0x04
0>

history information

Print out information about execution history.

$ ucsim_51
uCsim 0.9.10, Copyright (C) 1997 Daniel Drotos.
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.
0> load "remo.hex"
Loading from remo.hex
55755 words read from remo.hex
0> step 20

Stop at 0x000a13: (109) stepped 324 ticks
     R0 R1 R2 R3 R4 R5 R6 R7
     41 04 fc c9 8b bc 00 00
@R0 76 v  ACC= 0x80 128 .  B= 0x00
@R1 8b .  PSW= 0x01 CY=0 AC=0 OV=0 P=1
SP 0x27 -> 00 09 fe 01 77 1d 84 43
   DPTR= 0xff00 @DPTR= 0x04   4 .
0x0a13    2f       ADD    A,R7
F 0x000a13
Simulated 324 ticks (2.930e-05 sec)
Host usage: 0.000019 sec, rate=1.536000
0> history info
len: 10000
used: 20
insts: 20
0>

Len is the size of the history, used shows how many slots are filled, and insts is the number of the instructions recorded by the history.

history list [nr]
history print [nr]

This command is the same as the history command, but it accepts a parameter that specifies how many records to print (defaults to 10):

$ ucsim_51
uCsim 0.9.10, Copyright (C) 1997 Daniel Drotos.
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.
0> load "remo.hex"
Loading from remo.hex
55755 words read from remo.hex
0> step 1000

Stop at 0x000201: (109) stepped 20568 ticks
     R0 R1 R2 R3 R4 R5 R6 R7
     12 57 fc c9 09 f0 12 bd
@R0 df .  ACC= 0x14  20 .  B= 0x00
@R1 41 A  PSW= 0x00 CY=0 AC=0 OV=0 P=0
SP 0x2a -> 01 ba 23 87 29 81 02 2d
   DPTR= 0x1257 @DPTR= 0x1f  31 .
0x0201    a3       INC    DPTR
F 0x000201
Simulated 20568 ticks (1.860e-03 sec)
Host usage: 0.000188 sec, rate=9.886698
0> history info
len: 10000
used: 1000
insts: 1000
0> history list 3
0x01fc    70 01    JNZ    0x01ff
0x01ff    e4       CLR    A
0x0200    93       MOVC   A,@A+DPTR
0> history list
0x0212    89 82    MOV    0x82 <DPL>,R1
0x0214    80 e3    SJMP   0x01f9
0x01f9    12 01 9f LCALL  0x019f
0x019f    ef       MOV    A,R7
0x01a0    65 82    XRL    A,0x82 <DPL>
0x01a2    70 03    JNZ    0x01a7
0x01a7    22       RET
0x01fc    70 01    JNZ    0x01ff
0x01ff    e4       CLR    A
0x0200    93       MOVC   A,@A+DPTR
0>

history clear

This command clears the history; it deletes all recorded elements.

$ ucsim_51
uCsim 0.9.10, Copyright (C) 1997 Daniel Drotos.
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.
0> load "remo.hex"
Loading from remo.hex
55755 words read from remo.hex
0> step 1000

Stop at 0x000201: (109) stepped 20568 ticks
     R0 R1 R2 R3 R4 R5 R6 R7
     12 57 fc c9 09 f0 12 bd
@R0 df .  ACC= 0x14  20 .  B= 0x00
@R1 41 A  PSW= 0x00 CY=0 AC=0 OV=0 P=0
SP 0x2a -> 01 ba 23 87 29 81 02 2d
   DPTR= 0x1257 @DPTR= 0x1f  31 .
0x0201    a3       INC    DPTR
F 0x000201
Simulated 20568 ticks (1.860e-03 sec)
Host usage: 0.001160 sec, rate=1.603413
0> history list 5
0x01a2    70 03    JNZ    0x01a7
0x01a7    22       RET
0x01fc    70 01    JNZ    0x01ff
0x01ff    e4       CLR    A
0x0200    93       MOVC   A,@A+DPTR
0> history clear
0> history info
len: 10000
used: 0
insts: 0
0>