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Text File | 1986-04-10 | 14.6 KB | 535 lines

EMU Processor Emulator EMU performs a software simulation of the target processor to enable the verfication of program logic. Software emulation cannot replace hardware emulation for testing aspects of your program which depend upon the timing of critical external events, or for interaction with real world devices. EMU does provide symbolic debugging of the logic portions of your program, and may thus prove convenient for testing those portions of your program before submitting the program to hardware for a full scale test. Input to EMU consists of an object file .HEX produced by the MACxx assembler, and an optional .SYM file which can be produced at the time of assembly. EMU looks for the .SYM file on the same disk drive as the hex object file. The symbol file can be produced by following the assembly option immediately (no space separating) with another drive specification: MACxx SOURCE.ABE creates the hex file on drive B,reading the source file on drive A. No listing or SYM files are produced. MACxx SOURCE.ABEB creates a symbol file on drive B as well as the hex file. The drive selected for the .SYM file should be the same as that selected for the object file if the symbol file is to be used by EMU. EMU is menu driven: at various stages of its operation you can bring up a menu and select from a suite of functions. The menu items are generally self explanatory however the following notes should augment the menu notes. The main control menu consists of: A Assemble B Set Offset Bias D Display Memory E Enter Memory F Fill Memory L Load Program M Move Memory Q Quit S Search Memory T Display Symbol Table U Disassemble Memory X Emulation Monitor = Evaluate Expression Response to the menu consists of one of the above characters, followed by a parameter list. You may enter your response in either upper or lower case. If a SYM file was accessed by program load, the parameter list can contain valid references to the symbol table. An invalid expression in the paramter list voids the entire list. Numeric parameters are default hex. If you wish to represent a decimal number it must be suffixed by t (for ten). Since EMU allows symbolic references, which must begin with an alphabetic character, numeric entries must begin with a digit. Thus FF represents the symbol FF, which may not be found in the symbol table, and 0FF repesents the hex value. L Load Program Program loading is cumulative, in that the workspace area and symbol table are not cleared before program load. You may therefore load individual program segments separately. If duplicate symbols exist in the separate load segments the expression evaluator will find only the last definition. QUIT At the outer menu level Q returns to the operating system. A Assemble The in-line assembler option allows you to enter instructions directly into memory. No symbols may be entered into the symbol table. Symbolic references are allowed only to those symbols learned from the .SYM file. A line beginning with a blank returns control to the main menu. B Set Offset Bias -2- The program space may be mapped into any address within a 64k space by the offset bias. You must execute this command if your program is to run outside the region bounded by 0 and the available memory limit. D Display Memory The display command is entered as: Dstart,end The end parameter is optional. The display will exhibit 16 bytes of memory if the end is ommitted. The start and end may consist of any valid expression using program symbols. The display will halt for key press after 15 lines. You may type ESCape to abort the display and return to the menu. E Enter Memory The enter memory command allows you to modify the workspace program memory. The command is entered as: Estart The display will present the current memory address and the current contents at that address. You may step over the current location without changing its contents by entering only a carriage return. Entering an 8 bit expression followed by a carriage return will store the value of the expression at the current address. You may abort the sequence by typing a period followed by a carriage return. F Fill Memory The memory fill command allows you to initialize a portion of the workspace -3- area. The command is entered as: Fstart,end,value The region between start and end inclusive will be filled with the byte value. M Move Memory The Move command allows you to move a block of workspace memory to another location. The command format is: Mstart,end,destination The block of memory from start to end inclusive will be moved to the destination location. S Search Memory The search function allows you to find a string of bytes in workspace memory. The command is entered as: Sstart,end,v1,v2,v3,...... The search will display all locations within the interval start-end which contain the sequence v1,v2,v3..... No such display implies that the sequence was not found. U Disassemble Memory -4- The disassemble command is entered as: Ustart,end If the second parameter is absent the display will continue until ESCape is entered. The program will display 15 lines of code, and then pause for keyboard input before continuing. You may return to the main menu by typing ESCape. X Emulation Monitor The emulation monitor allows the processor simulation to execute the program. The monitor begins by asking for the execution address. This is the address for which simulation will begin. You may respond with any valid expression. Next the monitor requests a string of breakpoint addresses. Up to 10 breakpoint addresses can be inserted in the program. The simulator will will check the program counter against this list before executing every instruction. If a match is found the simulator will enter the single step mode and display the instruction, and register values. If you wish to single step the program from the starting value you may type return as the response to the breakpoint query. Each breakpoint can be assigned a pass counter, the number of times the breakpoint must be reached before the break will be effected. The pass counter is assigned to a breakpoint by enclosing the pass count in parentheses after the breakpoint address. Thus in response to the breakpoint query you entry of: 100,200,300 will impose first pass breakpoints at locations 100H,200H, and 300H. Suppose you wish to allow the instruction at 200H to be executed, say, three times before the break is imposed. Your response in this case would be: 100,200(3),300 After the pass count is reached at 200H the break is imposed and the breakpoint is thereafter imposed at every instance the program reaches this location. Next the monitor requests a string of trap values. These are 16 bit values -5- which are to be tested against every instruction containing a 16 bit reference. If an instruction is found to contain a trap reference the simulator will enter the single step mode as if a breakpoint were reached. During the single step mode it is important to note that two instructions are displayed. The instruction just executed, and the next instruction to be executed pointed to by >. The status of the flags and registers is a consequence of the instruction(s) executed and not that highlighted by >. The program will run from the starting point without display until either a breakpoint or trap is reached, or until you type either ESCape,M,L,N,S,R,P, or G. ESCape aborts the simulator and returns to the main menu. While the program is free running typing L will cause the register display to be presented at each instruction, typing N will suppress the register display. Typing S will force the single step mode, and typing G will resume the free running mode. Typing P, followed by a hex value, allows you to force the program to execute at the PC corresponding to the new value. Typing R imposes a breakpoint at the next PC value. This selection is most useful in the single step mode to allow the emulator to skip over a subroutine CALL. The R command replaces the last breakpoint in your breakpoint list with the address of the instruction following the CALL, the single step and list flags are reset, and control is passed to the emulator allowing the program to free run until the return address is reached. Typing #nnn, where nnn is a valid expression, remember it is default hex, allows the emulator to run the next nnn steps, with display on but operator intervention turned off. Typing M enters the emulation menu program. The emulation menu presents a list of options in the manner of the main menu. The options available from the emulation menu include many of those from the main menu, and their manner of selection is identical. You may neither enter the emulation monitor nor load a program from the emulation menu. There are additional selections from the emulation menu which pertain to the execution of the program. A Show All Register Space The single step emulation display does not provide for the display of the entire register bank for some processors. This command allows you to view all the registers. B Reset Breakpoints -6- This option allows you to re-define the breakpoint list. All previous breakpoints are forgotten. D Display Memory (as in main menu) E Enter Memory (as in main menu) F Fill Memory (as in main menu) G Quit Single Step This command resets the single step flag. The program will execute in the free running mode when the menu is abandoned. The free running mode will continue until a break point is reached or until control is gained from the keyboard. H Trace History The emulator maintains a buffer of the last 16 instructions executed. You may examine this trace history by the H command. M Move Memory (as in main menu) P Set PC for next instruction You may force the emulator to resume execution at a new address. The pending instruction before forcing the new PC value is not executed. -7- Q Quit Menu Return to the emulator. R Set Registers You are prompted for the manner in which you may alter the current contents of the registers and flags. S Search Memory (as in main menu) T Reset Traps This option allows you to re-define the trap values. As with the breakpoint redefinition, all previous traps are forgotten. U Disassemble Memory (as in main menu) V Display Processor Status You may obtain a view of the current processor status by selecting the V item from the emulation menu. Remember that when you Quit the menu you will execute the next instruction of your program before you can get a chance to examine the processor. The V option allows you to examine the state before the next instruction. If you are in the single step mode, as opposed to interrupting the processor by typing M, the V display will duplicate what you saw just before entering the emulation menu. W Set Window -8- The processor status display allows for the definition of a memory window of 16 bytes length. This window is shown along with the register and timing display. You may position this window within the workspace area by the W command: Wvalue The window will retain this value. Z Zero Trip Cycles The emulator maintains two counters which accumulate the number of processor cycles during program execution. These counters are set to zero at entry to the emulation monitor. One of these counters can be set to zero at any time by the emulation monitor. PROGRAM INPUT/OUTPUT If the processor supports i/o instructions the simulator will call routines to gain input from the keyboard, or display output on the console. Program output requires a key press from the user before execution continues. If the program is free running at this time, typing ESCape will enter the single step mode. To enter the single step mode for a free running program locked in an input loop, you must type an invalid hex input, say carriage return, and receive the invalid prompt message. At this point you may type ESCape to enter the single step mode. Emulation Speed As a rough indication of the relative speed of the emulation program, a simulation of the 65Cxx series on a 5MHz 8086 yielded approximately 1000 simulated processor cycles per second. This is between one and two thousand times slower than the real execution speed. -9-