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emu48-mirror/DEBUGGER.TXT
Gwenhael Le Moine a6d5624a8b
2019-10-16: Updated to version 1.62 
Signed-off-by: Gwenhael Le Moine <gwenhael.le.moine@gmail.com>
2024-03-20 08:15:25 +01:00

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Debugger in Emu48/Tools/Debugger...
-----------------------------------
This is a short description of the internal assembly debugger of Emu48.
The debugger was designed to help customers inspecting assembler code objects, a part that cannot be handled satisfactorily by the JAZZ package. Thanks to Mika Heiskanen and all the others supporting this great program.
After starting the debugger the emulation will stop at the current program counter position. The emulation will continue after closing the debugger window. Please remember that the clock now shows the wrong time.
1.) System Menu / Debugger Settings
This is the configuration dialog for the debugger.
In the "Disassembler" section you can switch between HP and Class Mnemonics for the disassembler. This switch is exactly the same like in the main Settings dialog.
In the "Symbolic" section you can setup the debugger for symbolic debugging. Therefore the debugger needs a reference file. The reference file must contain a table for converting an absolute address into a symbolic name. I decided to use the HP-TOOLS object files (file extension *.o) with the supported entries. These object files are usually provided by HP for the HP48 and HP49 series and are necessary for linking object files. In the case of older calculators you have to make them by your own. Using the object file for the linker as reference has two disadvantages. First such an object file has an assembler specific output format, in our case the debugger only understands the output format of HP SASM v3.x. Second, in some cases an entries has two or more different names and I cannot control which name is returned.
Example from ENTRIES.A (HP48 Supported ROM Entry Points)
=UNROT EQU #60FAC *
=3UNROLL EQU #60FAC *
=XYZ>ZXY EQU #60FAC *
My implementation returns the last name inside the linker object file to the chosen address.
If you don't have the linker object file, the HP28S entry point list for example is only distributed as assembler source file SUPROM28.A, you can simply generate it with
sasm -N SUPROM28.A
- Enable
With an unchecked Enable check box you can disable the symbolic debugging without removing the reference file.
- Model
Each calculator model needs his own symbol reference file. The given models exactly corresponds to the one used in the KML script. When you opening the settings dialog automatically the actual model is chosen in the combo box. You can switch to all other possible calculator models to enter the corresponding reference files. When you exit the dialog with the Ok button all filenames are saved.
- Edit field
The edit field must contain the filename to the model specific symbol reference file which is chosen by the combo box.
2.) Menu Debug
- Run F5
Continue calculator emulation under debugger control. The emulation will stop at a breakpoint. Please remember that the emulation speed is slower than without debugger control.
- Run to Cursor F6
Execute program until address at cursor position is reached. Breakpoints are still active and may stop execution before.
- Step Into F7
Execute one code instruction.
- Step Over F8
Execute a GOSUB, GOSUBL or GOSBVL as one instruction. Normally the instruction cursor will set to the position behind the GOSUB instruction.
But this makes trouble in the following code part:
GOSUB +
NIBASC /Hello world/
+ C=RSTK
The program counter will never reach the address behind the GOSUB instruction. The debugger solve this problem by breaking the emulation when the stack has the same level before the GOSUB instruction. In this example the single step execution will continue after the C=RSTK instruction.
- Step Out F9
Continue the program until a RTI, RTN, RTNC, RTNCC, RTNNC, RTNSC, RTNSXN, RTNYES instruction is found above the current stack level.
At some code constructions (mostly used to save space on the hardware stack) like
C=RSTK
PC=C
and
C=RSTK
RSTK=C
RTN
the stop address will be wrong. The problem in both code fragments is the C=RSTK opcode. In the first example there is no RTN instruction to stop. In the second one the C=RSTK instruction purge the original return address and then the RSTK=C instruction is interpreted as a GOSUB instruction.
In opposite the following code will work fine:
RSTK=C
..
code <- F9 was pressed here
..
GOSUB -
C=RSTK
RTN <- emulation will stop after this instruction
- RTN
So be careful using the F9 key.
- Break F11
Stops the emulation at the current program counter position.
3.) Menu Breakpoints
- Set Breakpoint F2
Toggle a code breakpoint at the cursor position in the Code window.
- Edit Breakpoints...
You get a sorted list of all current breakpoints. When the breakpoint is checked it's enabled otherwise it's disabled. With "Add" you can add a new or enable an existing breakpoint, with "Delete" you can delete the selected ones. Addresses greater than #FFFFF are cut after the fifths nibble. When adding a new breakpoint, you must select if this is a "Code", "RPL", "Memory Access", "Memory Read" or "Memory Write" breakpoint.
- "Code" stop before opcode execution on this address
- "RPL" stop on the first opcode of the selected RPL address
- "Memory Access" stop before reading or writing to the selected address
- "Memory Read" stop before reading the selected address
- "Memory Write" stop before writing to the selected address
With a left mouse button double click on a breakpoint you can toggle the check box inside. When you use the space key instead, on all selected breakpoints the check box is toggled.
- Clear All Breakpoints
Clear all address specific breakpoints.
- NOP3 Code Breakpoints
What are NOP3 code breakpoints? As you know user programs are loaded somewhere in memory and can be moved after a garbage collection. So it's very difficult to break a user program at a hard set breakpoint with F2. To solve this problem the debugger will stop emulation at a NOP3 opcode. So you can easily add a NOP3 command into your sources to force a break condition. To enable this you have to check this item.
NOP3 and NOP3, what's the difference? The Saturn CPU has no NOP command, so NOP3 is an opcode that is three nibbles long and doesn't change a register. In the HP SASM.DOC document two different opcodes are defined for NOP3:
Opcode 820 for HST=0 0
and
Opcode 420 for GOC + (next line)
In the assembler of the HPTOOLS 3.x package NOP3 is defined as opcode 820. The advantage of the opcode is that the execution time is always the same, independent from the carry flag. This code is used in the HP48 ROM as well. So I decided to use the GOC opcode for a code breakpoint condition.
A short example how to use a NOP3 Code breakpoint:
ASSEMBLE
NIBASC /HPHP48-E/
BREAK MACRO
CON(3) #024 NOP3
ENDM
RPL
CODE
BREAK code breakpoint
GOSBVL =SAVPTR save register
GOSUB + problem for step over
NIBASC /Hello world/
+ C=RSTK
GOVLNG =GETPTRLOOP
ENDCODE
- CODE Object Breakpoints
If this item is checked, the debugger stops program execution at the first instruction of every DOCODE object which isn't located in ROM. For inspecting DOCODE objects in ROM use address CODE breakpoints instead please.
- RPL Breakpoints
If this item is checked, the debugger stops program execution on every instruction called after a PC=(A) or PC=(C) opcode. This is normally the begin of a new RPL command. RPL breakpoints use a "-R" marker instead of the assembler "->" PC position marker.
4.) Menu Interrupts
- Step Over Interrupts
If this item is checked, interrupt handler code will be skipped. This option is useful when you don't want to debug the interrupt handler. But be careful, when you disable the interrupts all code until interrupt enable belong to the interrupt handler code and couldn't executed in single step any more. Enabled breakpoints are still active.
You can also use this option if you want to quit the interrupt handler. Just check this option, press F7 for "Step Into" for stopping the debugger behind the RTI instruction, and uncheck this option again.
5.) Menu Trace
- Settings...
This opens a dialog to configure the trace file output.
The "Log File:" editbox contains the log output file. A filename without the file path save the file in the emulator installation directory.
For "File Mode" select "New" for creating a new empty trace file or select "Append" for appending the new trace output when trace is enabled. If you chosen "Append" and the trace file don't exists, a new trace file is created.
The "Logging" checkboxes "Register", "MMU" and "Opcode" determine the output content of the trace file.
"Register" enables printing the CPU register content in front of the disassembled opcode. For some, mainly size output reasons the content of the "Write Only Registers" are not shown.
"MMU" enables printing the MMU register content between register and disassembly.
"Opcode" enables the opcode output in the disassembled and if necessary in the following lines.
- Enable
If this item is checked, the file trace is enabled. Dependent on the "File Mode" setting, a "New" empty trace file is generated or in "Append" Mode additional data is appended to the current log file. Unchecking this item stops logging and flushing the trace file.
6.) Menu Info
- Last Instructions...
This is a short viewer for the last 255 executed CPU addresses. The disassembled opcode maybe wrong, because only the CPU address of each command was saved and memory mapping may have changed meanwhile. In the "Last Instructions" dialog you can copy selected lines to the clipboard or clear this list.
- Profiler...
This opens a small toolbox window which shows the number of CPU cycles and the corresponding execution time of the instruction sequence between the last two breakpoints. The CPU cycles are only approximate values, the real cycles are depending mostly on the used ROM to Saturn CPU core interface.
- Write Only Registers...
Some of the display registers have a different meaning on reading and writing. This dialog shows the data written to the write only I/O registers.
7.) Code window
This windows shows you the disassembled code. The line with the current PC is marked with a "->" or "-R" between the address and the disassembly.
You can use the UP, PAGE UP, DOWN and PAGE DOWN keys to scroll the window content. There is one strange behavior, when you move to higher addresses the debugger is able to disassemble the next line correctly, but when you move to cursor to lower addresses the debugger does not know if this address is at the begin or inside of an opcode. In result you get wrong disassembled lines.
Context menu pressing the right mouse button:
- Go to address... G
Moves the cursor to the specified code address. Therefore you can enter a hexadecimal number or the symbolic reference name.
- Go to PC
Sets the cursor to the actual position of the PC.
- Set breakpoint F2
Toggle a code breakpoint at the cursor position in the Code window.
- Set PC to selection
Set the PC to the cursor position. Be careful with this command, you change the execution order of the commands!
- Find
Search in the mapped CPU address area for an address which contain a PCO (Primitive Code Object) header. The disassembled code of this address is shown in the Code window.
- Previous PCO
Search for a PCO before the address shown in the first line of the Code window.
- Next PCO
Search for a PCO behind the address shown in the first line of the Code window.
8.) Register window
Here you can see the actual contents of the CPU registers. The values are only updated at a program execution stop. All changed CPU registers are highlighted.
With the left mouse button you change the content of the register. On bit registers, like CY and Mode, the state change immediately without any request.
9.) Memory window
This windows shows the memory content in the selected context.
You can use the arrow, PAGE UP and PAGE DOWN keys to move the cursor to a memory position, the + and - keys change the memory position by one nibble under the cursor. With a double click on the left mouse button (only in Map mode) you can change the content of the two addresses. When the memory position is read only (ROM or write protected RAM) the content wouldn't change.
Context menu pressing the right mouse button:
- Go to address... G
Moves the cursor to the specified memory address. Therefore you can enter a hexadecimal number or the symbolic reference name.
- Go to PC
Sets the cursor to the actual position of the PC.
- Go to D0
Sets the cursor to the actual position of the D0 register.
- Go to D1
Sets the cursor to the actual position of the D1 register.
- Go to Stack
Sets the cursor to the return address placed in the top level of the stack.
- Follow
Follow is a Pop-up menu to change the address behavior of the memory window. Normally the address of the memory window is static and only change by entering a new address. With Follow the memory window view follow the content of a selected address or register. In follow mode the memory window is only updated after an emulation step.
- Follow none
This is the default mode. The address of the memory window is static.
- Follow Address Content
This is a special mode of indirect addressing. You can specify an address which content will we interpreted as memory pointer. The memory window follow this memory pointer.
- Follow Register PC/D0/D1
The Memory window follow the content of the selected register.
- Find... F
Calls the "Find" dialog box, allowing you to search for a data sequence in hexadecimal or ASCII mode. The search area is selected by the memory view Mapping mode described in the following section. If the data sequence is found the Memory window and an opened "RPL Object Viewer" window will be updated.
With the button "Previous" you can search for the previous and with the button "Next" you can search for the next occurrence of the data sequence.
When you close the "Find" dialog box, you will loose all saved strings in the data combo box.
- Mapping
Mapping is a Pop-up menu to select the memory view of the Memory window. Normally the CPU see only 512KB of the total memory, the rest is banked or covered by other modules. The following menu entries select the memory chip connected with the chosen Chip Select signal of the MMU. The connections are calculator model dependent.
- Mapping Map
This is the default mode. Here the Memory window shows what the CPU see. In this mode you can also change the memory content of writeable memory.
- Mapping NCE1/NCE2/CE1/CE2/NCE3
Here the Memory window shows the content of the selected Chip Select signal. The content is showed in a linear address model and it's content can't be changed in this mode.
Here's a comparison of the mapping of the emulated calculator models:
Abbreviations: ROM = Read Only Memory
RAM = Random Access Memory
Flash = electrical reprogramming ROM
Slt = Memory Card Slot
BS = Bank Switcher (no memory)
nc. = not connected
| HP38G | HP39/40G | HP48S/SX | HP48G/G+/GX | HP49G
-----------------------------------------------------------------------------
NCE1 | ROM 512KB | ROM 1024KB | ROM 256KB | ROM 512KB | Flash 2048KB
NCE2 | RAM 32KB | RAM 128KB | RAM 32KB | RAM 32/128KB | RAM 256KB
CE1 | nc. | BS | Slt1 32/128KB | BS | BS
CE2 | nc. | nc. | Slt2 32/128KB | Slt1 32/128KB | RAM 128KB
NCE3 | nc. | RAM 128KB | nc. | Slt2 32KB-4MB | RAM 128KB
- Load Memory Data...
The "Load Memory Data" dialog box allows loading memory dump files to the specified address inside the Saturn address area. The specified address must point to RAM, writing into ROM areas isn't possible. The memory dump file must be in packed data format, meaning each byte in file contain two Saturn data nibbles with the low nibble containing the even and the high nibble the following odd address. The disadvantage of packed files is that you cannot load memory files with an odd number of data nibbles, but the advantage is that you can directly load an assembler output to memory.
- Save Memory Data...
The "Save Memory Data" dialog box allows saving the data of the specified Saturn address area into a memory dump file. The memory dump file contain the data in packed data format, meaning each byte in file contain two Saturn data nibbles with the low nibble containing the even and the high nibble the following odd address.
- RPL Object Viewer...
This opens a small toolbox window showing the decompiled RPL object in the selected memory map mode at the memory address marked by the cursor. If the toolbox window is already open the content will be updated. There's a problem if you want to select an address inside the marked two addresses. The easiest way to switch the address is the use of the + and - keys changing the memory position by one nibble under the cursor.
10.) Stack window
The content of the hardware stack is viewed here. In "1:" is the current return address. A double click on an item shows the address content in the Code window.
Context menu pressing the right mouse button:
- Push
Push a new element before the current selection onto the stack.
- Pop
Pop the selected element from the stack.
- Modify
Modifies the stack content of the current selection.
11.) MMU window
The configuration of the memory controllers is viewed here. The viewed addresses are the first address of each module area and may differ from the given address in the CONFIG command.
This example
LC(5) #C0000 128KB size
CONFIG
LC(5) #98765 start address of module
CONFIG
will config a 128KB module at address #80000 and not at the given address. So the MMU viewer will show you the address #80000.
12.) Miscellaneous window
The Miscellaneous window show you the internal state of the interrupt flag, the 1ms keyboard handler and the contents of the Bank Switcher latch. The Bank Switcher item is only enabled on calculators with a latch inside. You see the loaded value of the address lines A6-A0. You have to ignore the last bit (A0), because it isn't wired to the six bit latch.
You can change the values by pressing the left mouse button over the old content.
08/12/19 (c) by Christoph Gie<69>elink
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