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1. Bi 1bit audio out lt P3 72 gt home rst Illustration 17 1 bit audio output The 1 bit audio output is wired to the P3 7 pin of the 8051 When enabled the simulator will generate a 8 bit 44kHz mono PCM RIFF wave file of the name audioout wav in the current directory The file is created on the next step after the option is selected The file is kept open until the simulator is closed 24 2 6 The Options View Cn cd ycprojiemu8051 Release emu8051 exe Options Di Hardware super 8051 gt Clock at 12 606 MHz gt Stack exception enabled gt Illegal opcode exception enabled gt home rst Illustration 18 The options view The options view can be used to alter the behaviour of the simulator The following additional keys are available Key Description Up and down cursor keys Toggle focus between different options in the options view Left and right cursor keys Change values of the different options The following options are available Option Description Hardware selection As of this writing only the super 8051 profile is supported Clock speed In addition to several pre set speeds the clock speed can be set to a custom value by selecting the right most option Input pin behaviour If output levels are low the read high input pins may act differently on different hardware It is advisable to keep the output pins high for the pins that are read T
2. 38 Other than the couple missing features and different 8051 variant profiles support for more advanced 51 variants with additional opcodes and faster clocks could be added Other development ideas include Bug fixes Graphical implementation of the front end with real time audio output Support for specific 8051 hardware profiles Support for 128B internal memory is already there so normal 8051 profile for instance should not be difficult Same goes for existence and size of external memory Loading and saving of external memory contents New logic board widgets Different sized character displays Graphical displays More than 1 bit audio Analog feedback circuitry Refactoring of logic board widgets into their own emulation cores Better configurability of logic board widgets The possibility to set the pins into which the widgets are connected to Logic board mode lock where user can go back to main view but port reads are still done from logic board widgets JIT compilation of 8051 code to an array of x86 function calls 39 References 1 MCS 51 microcontroller family user s manual Intel corporation Order no 272383 002 February 2004 2 80C51 family programmer s guide and instruction set Philips Semiconductors 1997 Sep 18 3 80C51 family hardware description Philips Semiconductors 1997 Dec 01 4 80C51 family architecture Philips Semiconductors Mar
3. can be used to load an object file Note that the file name may not contain spaces Most options have two forms a longhand and a short alternate form Available options are Option Alternate Description step instruction si Step one instruction at a time The default behaviour is to step one CPU cycle at a time noexc_iret sp nosp Disable SP iret watch exception noexc_iret_acc noacc Disable ACC iret watch exception noexc iret psw nopsw Disable PSW iret watch exception noexc acc toa noaa Disable acc to a invalid instruction exception noexc stack nostk Disable stack abnormal behaviour exception noexc invalid op noiop Disable invalid opcode exception iolowlow If out pin is low hi input from same pin is low Default is high Can be used to simulate problems with hardware iolowrand If out pin is low hi input from same pin is random Default is high Can be used to simulate problems with hardware clock value Set clock speed in Hz Please see the chapter 2 6 Options view for more detailed description on most of the options 2 2 Global Keys The simulator has several global keys that work regardless of the viewing mode Key Description Function keys Ouick switch between views V Cycle between views K Set breakpoint When the simulation reaches the breakpoint the simulation is stop
4. 66 66 AA HA AA 66 46 HA 66 AA AA KA 66 66 AA HA 66 AA HA HA lt gt Breakpoint Lov 6 A Breakpoint cleared Cycles Time Press any key to continue HW Super8051 PC Opcodes fss 4094 Ai 57 6008 6008 6008 6008 BAAR 6008 6008 6608 BAAR Illustration 22 Breakpoint cleared dialog The breakpoint cleared dialog appears when the user presses K again after a breakpoint is set The user can return to normal mode by pressing any key 30 2 7 5 The Reset Dialog cproj emu8051 Release emu8051 exe N SP PW P1 P2 P3 IP IE AA OA 46 HA 66 AR 66 AA AA OA AA AA 66 OA AA AA 66 66 66 AA AA OA AA AB lt gt lt l U J eSeeooaogdc OOS assosioi N Set PC Lov4999 Reset Cinit regs set PC to zero Cycles Wipe Cinit regs set PC to zero clear memory Time HW 6660 6660 6606 6686 4600 4660 6660 6660 6666 6666 Illustration 23 The reset dialog The reset dialog appears when the user presses the home key The following keys are available Key Function S Sets the program counter to zero everything else is kept unchanged Resets the 8051 state to default reseted state but does not wipe the memory This is what happens on normal hardware reset W Performs normal reset and wipes the memory as well Any other key Noreset is performed 31 2 7 6 The Exception Dialogs Cn cd wcprojiemu8051 Release emu8051 exe SP P0 P1 P2 P3 IP IE 66 AA 66 KA 66
5. CS AIIZ ALON N EE GE EE N Ee 35 32 Em lation Core N OTOS ed RE NG maanosa yhen GE Ge ee REG es 36 3 3 Simulation Front End NOTES uses ed ese ee ese taina ssa es sd ee ee laakamadot 37 3 4 Further Development Ideas siese bon havaata ee ige Eie ek es ge Vastaa NE N eke 37 Relerenoesiss EE E E E S E EE E S S An amma aan 39 1 Introduction The em8051 project was performed in EVTEK Polytechnic in 2006 to replace an older 8051 emulator that was in use in the school Primary new functionality over the old emulator was the need to support timer interrupts Further goal was to add support for all kinds of features that could be used to simulate school lab experiments without the real hardware at hand 1 1 What em8051 Is em8051 is a software simulator of the intel MCS 51 microcontroller architecture 1 Its goal is to be a free software simulator capable enough to help the development and debugging of 8051 based applications While the em8051 executable is useful as is source code is also provided so that additional features can be added for example to simulate different kinds of hardware configurations While effort has been made to make this program as flawless as possible there are bound to be some problems em8051 consists of Highly portable emulation core including Full 8051 instruction set Timer 0 and timer 1 modes 0 1 2 and 3 Interrupt priorities Debugging exceptions for invalid instructions odd
6. Contains handlers for disassembling opcodes opcodes c Contains handlers for emulating the opcodes The simulator front end is split into several source files The basic idea is that the main source file contains the global information and all the views have their own source files Source file Description emu c Main front end source Contains most of the global data miscellaneous utility functions and the main loop popups c The source code of all of the different pop up windows mainview c editor Main view related code and data including the small memory logicboard c Logic board view related code and data Also contains the implementation of all the additional simulated hardware memeditor c Memory editor view related code and data options c variables for options Options view related code and data Also contains the global Additionally the emulation core and the simulator front end have one header file each for global information 36 3 2 Emulation Core Notes The emulation core was written to be as independent of the environment as possible There are no memory allocations and the interfaces are very simple There is no global data and the source code is ANSI C for maximum portability Emulation accuracy was valued over emulation speed All of the data used by the emulator is stored in one structure It would be trivial to simulate several 8051 core
7. Play ss DE GE a mime T E a N 10 2 3 3 The Miscellaneous Display se is se SR DE ee Ge ee 11 2 3 4 The Execution DISDIA Vida Sad N Ge aai 12 2 3 5 The Common Registers B dien so EG REG DE IEN vasaa 13 2 3 6 The Control Registers and the Output Ports Display esse esse esse se ee 14 2 3 7 The Machine Status Word DisplaY esse se se an RA naene 15 24 The Memory Editor VIEW ss des nue ees TAS Sar ides aaa at 16 2 5 The ooie Board VieWe AG ee Ee ee miset 17 2 5 1 The 7 Segment DisplaS GE ESE ER Deeg 18 22 Lhe 8 Bit Shift Registers ss RE EE EG EE N Ge EG Ge Ge 19 2 5 3 The 44780 Style 2x16 Character DisplaY u esse sesse esse RA Re ee ee RA ee 20 2 5 4 The 1 Bit Audio OUDE EE SE EE Rates EG ED Se 23 2 6 The Options VIE EER AE N GE N GE EE A Ina 24 2 1 Pap Up Dialogen Na AN OE GE DR his 26 2 7 1 The File Name Entry idlop GE EG GE GE Ge 26 2 71 2 Fil Loading Error Dialoo8 in SE Dee se ss ee Sag ee en ee is nierien 27 2 7 3 The Set Program Counter And Breakpoint Setting DialogS iese esse see 28 2 7 4 The Breakpoint Cleared Dialog is ee GO AR n Se Ge NS 29 2 7 9 The Res t Dilo Se RE SE EG N EG Go De ge ain 30 2 16 The Exception DialOSd ae S TN N EG Ee Ee AI TAS TARTTIS 31 2 11 Lie Poit Re d Diallo se DO DE Ga se ints els 32 2 7 8 The Custom Clock Speed Entry Dialog s ssssssssesseeseesseesreseesseesrssessseesees 33 2 1 The Help Dialog SS EE Ee se SG DE dee GE SN 34 DPC laternals OP SMS VS det RE N GE aa 35 Del SOURCE
8. generated for the following reasons Bad file format if the file format is not recognized Unsupported HEX file version if the HEX file contains unsupported blocks such as 32 bit segments Checksum failure if the file appears corrupted No end of data marker found if end of file is reached before the object is completely imported 28 2 7 3 The Set Program Counter And Breakpoint Setting Dialogs N Ch ycprojiemu8051 Release emu8051 exe SP PM P1 P2 P3 IP IE 66 66 66 66 AR AA 66 66 AA HA 66 AA AA HA 66 66 AA HA 66 66 AA HA 66 66 AA HA lt gt A SDOO0008x7 SS5595050 OOOO SESEEESSv AN TMOD TCON TH9G TL8 TH1 TL1 SCON PCON aa 15 Lov G Cycles Time H HW S 66 66 66 66 R90 R1 R2 R3 R4 R5 R6 R7 B DPTR BAAR Bi 57 66 66 AA HA alala 6666 Bi 57 66 66 KA 6686 BAAR Bi 57 AJMP 48 4668 BAAR Bi 57 AJMP 66 alala 6666 AJMP 1215 4666 AJMP 66 Illustration 21 Set program counter dialog The set program counter dialog appears when the user presses the G key Similar dialog for setting the breakpoint appears with the K key The user can edit the program counter value by using the backspace key to remove the existing value and using the numeric keys and letters A to F to enter a new value The disassembly for the desired address is displayed 29 2 7 4 The Breakpoint Cleared Dialog Cn cd wcprojiemu8051 Release emu8051 exe SP PA P1 P2 P3 IP IE 66 AA AA KA
9. opcode is found the simulator breaks execution If disabled the opcode is considered a NOP Please note that the options can also be set using command line flags 26 2 7 Pop Up Dialogs em8051 displays various pop up windows for data entry or to convey information 2 7 1 The File Name Entry Dialog N Ch ycprojiemu8051 Releaseiemu8051 exe SP P0 P1 P2 P3 IP IE 66 AA AA KA 66 AA AA HA AA 66 AA HA 66 66 AA HA 66 AA AA HA 66 66 OA HA lt gt A Lov A Cycles Time N HW 46 66 66 66 66 R R1 R2 R3 R4 R5 R6 R7 B DPTR alala 66 aa alala 6680 aa 46 4900 6668 48 68 6668 AAR 46 aa alala 6606 48 6660 68 Illustration 19 File name entry dialog The file name entry dialog appears when the user presses the L key The user can use normal character keys to enter the desired file name and press enter to load the file Backspace key can be used to remove the existing text 27 2 7 2 File Loading Error Dialogs Stck SP PA P1 P2 P3 IP IE ACFGR1 RAOu P lt gt EET EE EE EE EE EE TMOD TCON THG TLB TH1 TL1 SCON PCON Load error File not found Press any k to continue PP PC Opcodes Assembly R0 R1 R2 R3 R4 R5 R6 R7 B DPTR lt gt lt Illustration 20 File not found dialog The file not found dialog appears if the entered file name does not correspond to any existing file The user can return to the normal mode by pressing any key Similar pop ups are
10. port bit is active the corresponding segment is lit 12 4 49 2 62 0 3 s 8 7 DE SE 17 5 689 13 2 0 52 ie EN IE 1 4 055 U al Le 12 ae d ON 91 4 055 1 5 1 Illustration 12 7 segment display 6 The pins have been mapped to segments as follows Pin Segment Pin Segment Pn 0 A Pn 4 E Pn 1 B Pn 5 F Pn 2 C Pn 6 G Pn 3 D Pn 7 DP 19 2 5 2 The 8 Bit Shift Registers cx d vcproj emu8051 Release emu8051 exe El 15 15 mea Shit shift registers gt ispe step Wunning Illustration 13 8 bit shift registers The 8 bit shift registers simulate a 74LS164 connected to the 8051 in the following manner VCC QA QB ___ C Pn 1 Cik ED A QF Pn 0 B OH 8051 TALS 164 Illustration 14 74LS164 connection diagram 8 em8051 simulates 16 shift registers connected to all of the output pins of the 8051 Each register takes two output pins The lower of the two is used as data and the higher as clock The shifting is performed on rising edge of the clock signal 20 2 5 3 The 44780 Style 2x16 Character Display Cn Cd ycprojiemu8051 Release emu8051 exe ELLO WORLD Second Row Display on Cursor on Blinking off 4bit off 4b tick 9 Busy mea 16x2 44786 displa gt Illustration 15 The 44780 style 2x16 character display The 44780 style character display emulatio
11. stack behavior or messing up important registers in interrupts Intel HEX file loading ncurses based text mode UI including Single stepping and various speed run modes including real time if host is powerful enough Debug breakpoint Main view with memory stack opcode and disassembly history view of most registers cycle and real time counters Memory editor view which shows all five types of memory at the same time logic board view with ports PO P3 wired to leds and switches plus optional additional widgets including 7 segment displays and 44780 like character display Options view where user can disable exceptions and set the desired clock speed 1 2 What em8051 Is Not em8051 does not attempt to be a hardware emulator in a way that no sub clock actions are emulated For instance the MUL AB instruction which takes four CPU cycles or 48 clock oscillations executes on the first cycle and then waits for the rest of the operation This may cause some slightly errornous timing behavior The logic board components especially the 44780 based 2x16 character display have been given much lighter treatment than for the 8051 core itself 1 3 Legalese This document is released under the creative commons Attribution 2 5 license See http creativecommons org licenses by 2 5 for details em8051 including the front end is released under the MIT license Copyright O 2006 Jari Kom
12. AA AA HA 66 66 46 HA 66 AA AA HA 66 AA AA HA 66 66 HOA HA lt gt A Lov N Breakpoint reached Cycles Time HW Supe PC Opcodes fssembly 6666 Bi 57 AJMP 605 7h ag AAAB 6068 AJMP 0057h 66 6008 6600 AJMP 0057h 90 6668 6668 AJMP 0057h 1515 6666 AJMP 0057h 66 AJMP 0057h 68 s pc step Illustration 24 Breakpoint exception dialog The exception dialogs appear when the simulation reaches some exceptional situation The user can return to the normal mode by pressing any key Exception dialogs exist for the following situations Breakpoint reached Stack exception Acc to a mov operation attempted PSW not preserved over interrupt SP not preserved over interrupt ACC not preserved over interrupt Invalid opcode reached The user can disable all of the exceptions separately in the options view 32 2 7 7 The Port Read Dialog Cn cd ycprojiemu8051 Release emu8051 exe SP PM P1 P2 P3 IP IE AG FF 1F 66 09 15 FF 1F 66 AA 8 FF iF 66 66 15 FF 3F 66 HA 15 FF 3F 66 HA 15 FF BF HA lt gt F 15 8 8 15 15 6 TL TH1 TLi SCON PCON 4 a 4 aa 15 port read Low6666 A A 6616866866666 Cycles Time H s HW Super8051 PC Opcodes fssembly 0022 12 LCALL 6062h BAAR 0092 CLR P3 7 6008 6664 CLR P3 6 6688 6646 SETB P3 5 BAAR 6668 MOU Pi FFh 6608 SETB P3 7 spc step Illustration 25 Port P1 read dialog The port read dialog appears when the execut
13. E 09 FF FF FF 09 FF FF FF 07 FF FF FF 09 FF FF FF 09 FF FF FF gt 07 FF FF FF 68 66 AA aa 66 00 66 66 46 86 66 66 aa 66 66 aa 66 66 Illustration 7 Control registers and output ports displays Two of the remaining displays show the state of the control registers and output ports and several lines of history The current values are displayed at the bottom The values are not editable directly but the user can use the memory editor to change the values of these registers 15 2 3 7 The Machine Status Word Display cx d vcproj emu8051 Release emu8051 exe Illustration 8 Machine status word display The top right corner display shows the state of the processor status word bits and several lines of history The current values are displayed at the bottom Field Description C Carry AC Auxiliary Carry FO User definable flag 0 RI Register Rx bank selection bit 1 RO Register Rx bank selection bit 0 Ov Overflow User definable flag P Parity 16 2 4 The Memory Editor View cx d lvcprojiemu8051 Release emu8051 exe 8 3 4 5 6789 running i home rst Illustration 9 The memory editor view The second view shows all of the five memory areas at the same time The following additional keys are available Key Description Tab Toggle focus between different editors in the memory editor Cursor keys page up Navigate within the currently active e
14. EVTEK Polytechnic em8051 a software based simulator of a 8051 based CPU IT Project Jari Komppa TM04S Supervising instructor Anssi Ikonen 14 May 2006 EVTEK AMMATIKORKEAKOULU TIIVISTELM Tekij Jari Komppa Otsikko em8051 ohjelmistopohjainen simulaattori 8051 prosessorille Sivum r 39 sivua Aika 14 5 2006 Koulutusohjelma Tietotekniikka Opettaja Anssi Ikonen K ytt ohjeet sek osittain tarkempi spesifikaatio emu8051 ohjelman toiminnasta Hakusanat 8051 8052 44780 mikroprosessorit elektroniikka assembly EVTEK POLYTECHNIC ABSTRACT Author Title Pages Date Degree Programme Jari Komppa em8051 a software based simulator of a 8051 based cpu 39 14 5 2006 Information Technology Teacher Anssi Ikonen Usage instructions and partially more detailed specification of the emu8051 simulator Keywords 8051 8052 44780 microprocessors electronics assembly Contents 1 LTO OTOS aines S ES EE DE EE EE DE N GE SE ED N ASS 3 ln WV eat onde oo IS ESE N ED EE Tt Naa RE GE N estes ee Eie 3 2 Wha tem8 OSL IS Notico SE GR ee a aa E a aa s 4 15 se CALC SC sian ies RES ea ie a ei De E aie E ee ails 5 DIMI STV uie IE SA LE OE it va 6 2 1 Launching ems sa ER SE EE GR N ES RD GE et rr et a ee 6 DPD CO BARKS Mm ON N DE EE OE RR nanna ne 7 iis be M VIER se EE Ge a e a AEE a 8 2 3 1 The Small Memory Editor sd Re ee aaa Se ei 9 23 2 Th Stack DIS
15. are focused the name of the currently edited register is shown instead of the address In addition to this the elapsed clock cycles and elapsed real time are shown along with the currently emulated hardware and clock speed The user can reset the cycles and time counters by pressing the End key 12 2 3 4 The Execution Display cx d vcproj emu8051 Release emu8051 exe PC _0pcodes fissembly 661D 31 97 ACALL 0197h 6197 66 NOP 0198 22 RET 661F 12 61 99 LCALL 6199h Illustration 5 The execution display On lower left is the execution window which shows the program counter operation codes and disassembly The lowest line shows the most recently executed instruction Changing the program counter through a reset or go to does not immediately alter the display 13 2 3 5 The Common Registers Editor cx d vcproj emu8051 Release emu8051 exe R R1 R2 R3 R4 R5 R6 R7 B DPTR 01 Ai 6668 01 Ai 4668 61 01 6686 01 Ai AAR 01 Ai 01 01 Illustration 6 Common registers editor On the right from the execution display are the common registers and several lines of history The current values are displayed at the bottom User can switch focus between the memory editor and the common registers with the tab key and edit the current state of the common registers directly 14 2 3 6 The Control Registers and the Output Ports Displays cx d lvcprojiemu8051 Release emu8051 exe SP PA P1 P2 P3 IP I
16. ch 1995 5 CFAH1602B NYA JP data sheet Crystalfontz America Inc 6 Kingbright SA 52 11 EWA data sheet Kingbright 22 Dec 2002 7 HD44780U data sheet Hitachi no version information 8 DM74LS164 8 Bit Serial In Parallel Out Shift Register data sheet Fairchild August 1986
17. ditor and page down Numbers and A F Edit the currently active value The editors work the same way as with the main view small memory editor with the additional feature of showing the current ASCII value of the contained bytes Non printable characters i e Those outside the ASCII range 32 126 are displayed as periods 17 2 5 The Logic Board View cx d vcprojiemu8051 Release emu8051 exe board view 46 g lt No additional hw gt Illustration 10 The logic board view The logic board view simulates a simple logic board with all of the 8051 output pins connected to LEDs and input pins connected to switches The following additional keys are available in the logic board view Key Description Up and down cursor keys Toggle focus between different parts of the logic board view Left and right cursor keys Change value of the additional hardware field Numbers 1 8 Switch the currently active port input pin on or off Some additional hardware widgets can also be connected to the 8051 using the logic board view The following chapters go through these widgets in detail 18 2 5 1 The 7 Segment Displays cx d vcprojiemu8051 Release emu8051 exe RE 15 15 a 7 seg displays gt spc step Wunning Illustration 11 The 7 segment displays The four 7 segment displays are wired to the four output ports in high active mode i e If the output
18. his option can be used to simulate possible problems Step mode The simulator can step a single CPU cycle 12 clocks for the 8051 or one single instruction 1 to 4 CPU cycles Interrupt handler SP The simulator can detect whether SP is not preserved by an watch exception interrupt handler and break the execution This behaviour can be disabled with this option 25 Option Description Interrupt handler ACC watch exception The simulator can detect whether ACC is not preserved by an interrupt handler and break the execution This behaviour can be disabled with this option Interrupt handler PSW watch exception The simulator can detect whether PSW is not preserved by an interrupt handler and break the execution This behaviour can be disabled with this option The user flags in PSW are ignored Acc to a opcode exception The Intel data sheets list acc to a move as an illegal instruction The simulator can detect this and break the execution This behaviour can be disabled with this option Stack exception The simulator can detect odd stack behaviour and break execution If the stack grows to upper memory but there is no upper memory or a push or pop instruction wraps around the memory the exception is thrown This behaviour can be disabled with this option Illegal opcode exception The 8051 instruction set has a single illegal opcode If this
19. ion reaches a point where the simulated application is reading from a port This dialog does not however appear in the logic board view Instead the values are read from the logic board The dialog also shows the bit pattern of the currently entered value The user can use backspace to remove the old value and use numbers and letters A to F to enter a new one The value is accepted by pressing enter 33 2 7 8 The Custom Clock Speed Entry Dialog Options Hardware super 8051 gt ea Clock at 6 100 MHz gt High inputs from ports with low out level should be 1 gt Enter custom clock speed mr 199900 1 Interrupt Interrupt handler psw watch exception enabled gt Acc to a opcode exception enabled gt Stack exception enabled gt Illegal opcode exception enabled Illustration 26 Enter custom clock speed dialog The enter custom clock speed dialog appears when the user selects the rightmost option in the clock speed option in the options view The user can enter a custom clock speed in Hz Backspace can be used to remove the current value and number keys can be used to enter a new value The value is accepted by pressing enter 34 2 7 9 The Help Dialog Cn Cd ycprojiemu8051 Releaseiemu8051 exe SP PA P1 P2 P3 IP IE 66 66 HO 66 AA HA AB FF 38 FF 1F 66 HA 25 66 66 66 AA AA GB FF 38 FF 1F 66 AA 66 66 HO 66 AA HA B FF 38 FF 3F 66 HA AA 66 HO 66 AA HA B FF FF FF 3F 66 HA Emulator v 0 7 htt
20. n is wired to the emulator in the following manner 8051 Pin 44780 Pin P1 0 P1 7 DBO DB7 P3 7 E or EN P3 6 RS P3 5 RW The simulation functions on the falling edge of the E signal for write operations and on the rising edge of the E signal for read operations This is slightly different from actual hardware RS R W t Illustration 16 CFAH1602B NYA JP read operation timing 5 21 On actual hardware depending on the speed of the 8051 host the order of functional operations may need to be somewhat different for them to work The way the chip is simulated may not be the correct way but it appears to work on some test applications It is also possible to confuse the simulator by switching the RW signal while the E signal is high as then one E pulse will generate both rising and falling edge events Other differences compared to hardware include Initialization delay reguirements are not simulated the 44780 works instantly Cursor is not displayed Cursor state on off blink is displayed The simulated 44780 contains 128 bytes of display RAM and 64 bytes of character generation RAM Custom characters are not displayed Character map uses the ASCII characters from 32 to 126 Zero character is a space Other characters outside that ASCII range are displayed as guestion marks Timings of the simulated 44780 are as follows Busy flag reading genera
21. p iki fi sol Copyright lt c gt 20906 Jari Komppa h This help shift g Quit Load intel hex file cursors Move cursor Single step B 9 a f Adjust values Toggle run mode tab Switch editor focus Adjust run speed Reset tick time counter Change views Set or clear breakpoint Reset with options Go to address Cadjust PC gt D2 B5 SETB P3 5 66 66 HY HA HO HA AA HY AA HA HAHA 75 90 FF MOU Pi 66 66 AA AA AA AA AA AA AA HA AHAA D2 B SETB P3 7 66 66 OA 66 AA AA AA HO AA AA HAHA MOU A Pi 66 66 HO 66 AA AA AA BAAR Padda eek ad hef el Illustration 27 The help dialog from version 0 7 The help dialog appears when the user presses the H key The dialog shows the current version of the application along with a brief list of keys and what they can be used for The user can return to the normal mode by pressing any key 3 The Internals of em8051 35 The following chapters aim to give the reader a high level understanding of the internals of the em8051 software simulator 3 1 Source Organization The em8051 project is split into two logical sections the emulation core and the simulator front end It is possible to create new front ends using just the emulation core The core consists of only three source files Source file Description core c Main emulation source Contains most of the public functions and takes care of timer and interrupt services device resetting and Intel hex file loading disasm c
22. ped Pressing k again clears the breakpoint Current address is shown by default Use backspace to edit the value G Set the program counter value go to H Shows brief help L Load an Intel HEX format obj file Space Simulation step Depending on the options this steps a single CPU cycle or a single instruction An instruction may take more than one CPU cycle If in run mode pressing space exits the run mode R Toggle run mode In run mode the simulator executes CPU cycles automatically at desired speed Run mode is also terminated if space is pressed or some pop up event such as an exception occurs and Adjust run speed Various run speed modes are supported Home key Reset emulator Shows a pop up giving user the choice of reset style ranging from simply setting program counter to zero to a complete wipe of all memory End key Resets clock counter Useful for timing events for example from one breakpoint to the next Shift Q Quit em8051 2 3 The Main View cx d vcproj emu8051 Release emu8051 exe SP PA P1 P2 P3 IP IE a Low8666 N Cycles 372 Time GET TE HW Super8651 12 G6MHz PC Opcodes fssembly 661D ACALL B197h 6668 0197 NOP 6668 6198 RET 6668 001F 12 01 99 LCALL 6199h BAAR 0199 NOP 6606 ispe step Wunning Illustration 1 The main view The main view is designed to give as much information about the 8051 emulation state as possible Additional keys a
23. ppa Permission is hereby granted free of charge to any person obtaining a copy of this software and associated documentation files the Software to deal in the Software without restriction including without limitation the rights to use copy modify merge publish distribute sublicense and or sell copies of the Software and to permit persons to whom the Software is furnished to do so subject to the following conditions The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software THE SOFTWARE IS PROVIDED AS IS WITHOUT WARRANTY OF ANY KIND EXPRESS OR IMPLIED INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM DAMAGES OR OTHER LIABILITY WHETHER IN AN ACTION OF CONTRACT TORT OR OTHERWISE ARISING FROM OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE 2 Using em8051 The following chapters cover the usage of the em8051 in detail 2 1 Launching em8051 em8051 can be launched either without any command line parameters for default functionality or optionally with parameters that alter the defaults The command line format for the emulator is as follows emu8051 options file name Where options can be zero or more options and the optional file name parameter
24. s at the same time due to this structure Instruction decoding is performed using a function pointer table with one entry for each instruction The 8051 has 256 different opcodes but due to overlapping logic only 111 functions needed to be written Similar handlers exist for the disassembly of the opcodes Optimization wise the function pointer array is a major headache for branch prediction An alternate switch case implementation was also written but it did not show much difference in performance based on profiling JIT compilation of the 8051 opcodes into an array of x86 assembly calls might help but that is way outside the scope of this project The reset function builds the function pointer tables so it has to be called before attempting to run tick Each call to tick emulates one CPU cycle i e 12 clock cycles on 8051 The emulator has hooks for various features that are not used in the current simulation front end For instance a callback is made every time the external memory is accessed This would make it possible to simulate some hardware that is hooked to the external memory bus 37 3 3 Simulation Front End Notes While the emulation core is extremely portable the front end itself is only very portable The front end uses global data performs memory allocation and has dependencies in external libraries such as ncurses Since the simulator only displays text it was decided to make the simulator run in
25. tes no busy time Reading and writing of memory takes 200 microseconds Clearing of the memory takes 2 milliseconds Other operations take 250 microseconds While busy only reading of the busy flag is legal Other operations are ignored Shifting of the display may not match actual hardware especially when shifting to negative offsets 22 The following 44780 instructions are supported Instruction Implementation notes Clear display Clears display sets display offset to zero cursor position to zero Sets writing direction to increment as in HD44780 data sheet 7 Does not clear character generation RAM Return home Sets display offset and cursor position to zero Entry mode set Supported Display on off control Cursor not displayed but cursor mode and blinking mode displayed in a separate information display Screen off blanks the display Cursor or display shift Supported Function set 8 and 4 bit input modes supported Only 2 line output mode supported mode selection ignored Font type selection ignored Set CGRAM address Supported Custom characters not displayed but reading and writing of the data works Set DDRAM address Supported Read busy flag and address Supported Write data to RAM Supported Read data from RAM Supported 23 2 5 4 The 1 Bit Audio Output cx Cd veprojiemuB8051tRelease emu8051 exe testprogihello obj a
26. text mode For this reason the simulator uses ncurses a standard text mode full screen application library On Windows pdcurses was used instead since there is no ncurses port for Windows The ncurses library also makes it possible to run the simulator on a Linux shell either locally or over ssh or in a Mac OS X console Window resizing is partially supported the simulator is primarily designed to run in 80x25 character resolution Since most of the front end is UI code it is a rather tangled mess This is especially true for the main view which simply has a lot going on This could have been helped by writing the front end in C instead but that would have reduced the portability The fact that ncurses code itself is rather cryptic does not help matters Everything except the 8051 simulation itself is implemented in the front end code This includes the various run modes breakpoints and the simulation of the additional widgets in the logic board view 3 4 Further Development Ideas At the moment the emulator core lacks the following features Serial port support including the serial port interrupt Counter interrupts 8052 timer2 interrupt Since the emulator currently only supports the super 8051 profile there is currently nothing to hook the external counter pins to This could be fixed by inventing a new special function register or two and to hook into these through the logic board view somehow
27. vailable for the main view are Key Description Tab Toggle between different editors in the main view Cursor keys page up Navigate within the currently active editor and page down Numbers and A F Edit the currently active value M Switch between memory editor modes to view all five kinds of 8051 memory The following chapters go through each part of the main view in detail 2 3 1 The Small Memory Editor cx d vcproj emu8051 Release emu8051 exe Illustration 2 Small memory editor The small memory editor shows 64 bytes of memory at once and can be toggled between the five memory types of the 8051 using the M key Cursor keys page up and page down can be used to move cursor in the memory view and to scroll the visible memory area Number keys and the keys from A to F can be used to adjust memory values 10 2 3 2 The Stack Display cx d lvcprojiemu8051 Release emu8051 exe Illustration 3 The stack display The stack display shows the current state of the stack scrolling up and down depending on the stack pointer value 11 2 3 3 The Miscellaneous Display cx d vcproj emu8051 Release emu8051 exe Low4 666 606606661 6 372 Cycles Time A A3ims HW Super8651 12 MHz Illustration 4 The miscellaneous display The miscellaneous display below the small memory editor shows the address and bit mask of the currently edited byte When the common registers

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