Direct Calls, Returns From Routines | Texas Instruments MSC1210

Direct Calls

6.4 Direct Calls

Another operation that will be familiar to seasoned programmers is the LCALL instruction. This is similar to a “GOSUB” command in Basic.

When the MSC1210 executes an LCALL instruction, it immediately pushes the current PC onto the stack and then continues executing code at the address indicated by the LCALL instruction.

6.5 Returns From Routines

Another structure that can cause program flow to change is the “Return from Subroutine” instruction, known as RET in Assembly language. The RET in- struction, when executed, returns to the address following the instruction that called the given subroutine. More accurately, it returns to the address that is stored on the stack.

The RET command is direct in the sense that it always changes program flow without basing it on a condition, but is variable in the sense that where program flow continues can be different each time the RET instruction is executed, de- pending on where the subroutine was originally called from.

6.6 Interrupts

An interrupt is a special feature that allows the MSC1210 to break from its nor- mal program flow to execute an immediate task, providing the illusion of multi- tasking. The word interrupt can often be substituted with the word event.

An interrupt is triggered whenever a corresponding event occurs. When the event occurs, the MSC1210 temporarily puts the normal execution of the pro- gram on hold and executes a special section of code referred to as an interrupt handler. The interrupt handler performs whatever special functions are re- quired to handle the event and then returns control to the MSC1210, at which point program execution continues as if it had never been interrupted.

The topic of interrupts is somewhat tricky and very important. For that reason, Chapter 10 is dedicated to the topic.

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Texas Instruments MSC1210 manual Direct Calls, Returns From Routines, Interrupts

Contents

User’s Guide Important Notice MSC1210 Memory Organization Introduction to the MSC1210Basic Registers System Timing Addressing ModesSerial Communication Pulse Width Modulator/Tone Generator Analog-to-Digital Converter Serial Peripheral Interface SPI Additional MSC1210 Hardware Additional Resource Additional Features in the MSC1210 Compared to Clock Timing DiagramBoot ROM Routines Instruction-Set Quick-Reference Guide SPI/PWM/Flash Write Timing System Timing Interrupt Control 16−1 Pin Descriptions of the MSC1210 14−2 Chapter −1. MSC1210 Block Diagram MSC1210 Description −2. Pin Configuration of the MSC1210 MSC1210 Pin-Out −1. Pin Descriptions of the MSC1210 Pin # Name Description −1 Pin Descriptions of the MSC1210 Pin # Name Description 1 I/O Ports P0, P1, P2, and P3 AD7 Port Port Oscillator Inputs XTAL1 and XTAL2 Address Latch Enable ALE Reset Line RSTProgram Store Enable Psen External Access EA Enhanced 8051 Core −3. MSC1210 Timing Compared to Standard 8051 Timing Flash Memory Family Device CompatibilityHigh Performance Analog Functions High-Performance Peripherals Description Program Memory Data Memory Internal RAM Description Program Memory −1. Program and Data Memory Size MSC1210Y2 MSC1210Y3 MSC1210Y4 MSC1210Y5 −2. Program and Data Memory Addresses Data MemoryOn-Chip Extended Static RAM Sram On-Chip Flash Data Memory External Data Memory Internal RAM −2. MSC1210 Memory Map Register Bank Stack Register Banks Bit Memory Or execute Special Function Register SFR Memory Defines the MSC1210 SFRs −1. SFR Names and Addresses SCON0 Referencing SFRs Referencing Bits of SFRs Bit−Addressable SFRs SFR Types SFR Definitions SFR Definitions SFR Definitions SFR Definitions Can be generated automatically by the MSC1210 P0DDRL/P0DDRH Port 0 Data Direction Low/High Byte, Addresses GCL/GCM/GCH Gain Low/Middle/High Byte, Addresses D4H/D5H/D6H SFR Definitions SFR Definitions SFR Definitions Describes the basic register functions of the MSC1210 ADC Accumulator Registers Register Program Counter PC Data Pointer DPTR0/DPTR1 Stack Pointer SP Describes the various addressing modes of the MSC1210 Immediate Addressing Mode Example−1. MSC1210 Addressing Modes Direct Addressing Indirect Addressing External Direct Addressing Movx A,@DPTR Movx @DPTR,A External Indirect Addressing Code Indirect Adressing Describes the program flow of the MSC1210 ADC Conditional Branching Direct Jumps Consider the example Returns From Routines Direct CallsInterrupts Description System Timers Startup Timing −1. Standard 8051 Timing System Timing System Timers −2. MSC1210 Timing Chain and Clock Control Microseconds Timer Milliseconds Timer −4. System Timing Interrupt Control One Hundred Millisecond Clock Flash Programming Mode Power-On Reset Timing Normal-Mode Power-On Reset TimingStartup Timing Symbol Parameter Min Max Unit Psen Describes the timers of the MSC1210 ADC Using Timers to Measure Time How Does a Timer Count?How Long Does a Timer Take to Count? Width Width ∝s RD or WR StrobeMovx Duration SYS CLKs At 12MHz −1. Timer Conrol SFRs Timer SFRsSFR Name Description SFR Address Bit Addressable? Tmod SFR Mode −2. Timer Modes and Usage TxM1 TxM0 Timer Description of Timer Mode Instruction −3. Example of 8-Bit Auto-ReloadCycle Tcon SFR Bit Name Bit Address Explanation of Function Timer−4. Tcon 88 H SFR Initializing a Timer Reading the Timer Detecting Timer Overflow Timing the Length of Events Using Timers as Event Counters Using Timer 1 T2CON SFR Timer 2 in Auto-Reload Mode Timer 2 in Capture Mode Timer 2 as a Baud Rate Generator Describes serial communication using the MSC1210 ADC Description Setting the Serial Port Mode Function Length Period −1. SM0 and SM1 Function Definitions Mode Serial Mode 0 Synchronous Half-Duplex High four bits bits 4 through 7 are configuration bits −2. Serial Port Mode 0 Receive Timing-High Speed Operation Serial Mode 1 Asynchronous Full-Duplex −3. Serial Port Mode 1 Transmit Timing −2. Common Baud Rates Using Timer BaudRate + 32 @ Timer1OverflowBaudRate + Timer2Overflow BaudRate + 12 @ 256 * TH1 −3. Common Baud Rates Using Timer Serial Mode 2 Asynchronous Full-DuplexRcap 2H Rcap 2L + Baud Rate RCAP2HRCAP2L @ 11.0592MHz f OSC −6. Serial Port 0 Mode 2 Receive Timing BaudRate + 2SMOD @ fOSC Serial Mode 3 Asynchronous Full-Duplex −7. Serial Port 0 Mode 3 Transmit Timing Setting the Serial Port Mode Setting the Serial Port Baud Rate −4. Mode 0 Commonly Used Baud RatesTH1 = 256 − Crystal / 192 / Baud Baud Rate −5. Baud Rate Settings for Timer Desired Baud Writing to the Serial Port −6. Baud Rate Settings for TimerBaud Rate 33MHz clk 25MHz clk 11.0592MHz clk Kb/s Reading the Serial Port Describes the interrupts of the MSC1210 ADC JNB TF0,SKIPTOGGLE Events That Can Trigger Interrupts Interrupt/Event Addr Priority Flag Enable Priority Control−1.Interrupt Sources 10-4 Enabling Interrupts −2.IE A8 H SFR−3.EICON D8 H SFR −4.EIE E8 H SFR Polling Sequence −5.IP B8 H SFR Interrupt Priorities−6.EIP F8 H SFR Interrupt Triggering Exiting Interrupts Serial Interrupts Types of InterruptsExternal Interrupts −7.EXIF 91 H SFR Bit Name Explanation of Function Watchdog Interrupt Timer InterruptsAuxiliary Interrupts −9.AIE A6 H SFR −8.Clearing Auxiliary InterruptsAux Interrupt Type Method to Clear Interrupt −11. PAI A5 H SFR −10. Aistat A7 H SFRBit Name Explanation of Function Clear Interrupt −12. PPI Bits of PAI SFR PAIx Bits Explanation of Interrupt/Event Waking Up from Idle Mode −13. EWU C6 H SFR Register Protection Push PSW Push R0 Error − Invalid instruction Common Problems with Interrupts Tone Generator 11-3 Description 11-2PWM Generator 11-5 −1. Block Diagram Tone Generator ToneFrequency +1 −3. Timing Diagram of Tone Generator in Staircase Mode Tone Generator Waveforms PWM Generator −1. PWM Polarity ConditionsDuty Cycle = PWM Period +1 − PWM Duty/PWM Period +1 Condition Duty Cycle −5. Timing Diagram of a PWM Waveform This can be expressed in code as −2. Configuring the PWM for Tone Generation Stmt ‘C’ Source Code Assembly Source CodeExample of PWM Tone Generation −3. Statement Explanations Example of PWM Tone Generation Idling −5. Statement Explanations −4. Configuring the PWM for Tone Generation with PWM IdlingExplanation Example of Updating PWM −6. PWM Timing 11-12 PGA DAC 12-10 −1. MSC1210 Architecture −2. Input Multiplexer Configuration Input Multiplexer Positive Input Negative Input Temperature Sensor 12-6 Burnout Current Sources MSB Input Buffer Analog Input@ 10 ACLKFrequency −1.PGA Settings Programmable Gain Amplifier PGA Offset DAC Modulator Calibration Mode −2.Calibration Mode Control BitsCalibration Digital Filter −4. Filter Step Responses −5. Filter Frequency Responses Multiplexing Channels −3.Filter Settling−4.Output Data Rate and Channel Rate Samples to Discard Filter Voltage Reference −5.Output Data Rate and Channel Rate 10x faster Summation/Shifter Register Source Summation Count Shift Summation Count Manual Summation Mode ADC Summation Mode Manual Shift Divide Mode ADC Summation with Shift Divide Mode Interrupt-Driven ADC Sampling Analog-to-Digital Converter 12-21 Syncronizing Multiple MSC1210 Devices Analog-to-Digital Converter 12-23 Ratiometric Measurements ADC Result + V REFPT100 ADC Result + R REF @ I OUT Differential Vref 12-26 Clock Phase and Polarity Controls 13-4 SPI Signals 13-5SPI System Errors 13-6 Description 13-2 −1. SPI block diagram Functional Description −2. SPI Clock/Data Timing Clock Phase and Polarity Controls SPI Signals Master In Slave OutMaster Out Slave Serial Clock SPI System Errors −3. SPI Reset State Data Transfers 13-8 Fifo Operation −4. SPI Fifo Operation Code Examples SPI Master Transfer in Fifo Mode using Interrupts 13-12 Description 14-2 Watchdog Timer 14-4Low-Voltage Detect 14-2 −1. Brownout Reset and Low-Voltage Detection Low-Voltage Detect Power Supply −2.Comparator Specification−1.Typical Sub-Circuit Current Consumption −3.Band Gap Parameters Watchdog Timer Watchdog Timer Hardware Configuration Enabling Watchdog Timer Watchdog Timer Resetting the Watchdog Timer Disabling Watchdog Timer Watchdog Timeout/Activation Hardware Configuration 15-2 Power Optimization 15-9Advanced Flash Memory 15-6 Breakpoint Generator 15-7 Hardware Configuration Hardware Configuration Registers Hardware Configuration Register 0 HCR0 DFSEL2/1/0 Amount of Flash Data Memory Hardware Configuration Register 1 HCR1 Hardware Configuration Memory Accessing Configuration Memory in a User Program Advanced Flash Memory Updating Interrupts with Reset Sector LockWrite Protecting Flash Program Memory Configuring Breakpoints Breakpoint Generator Breakpoint Auxiliary Interrupt Disabling a Breakpoint Power Optimization Flash Memory as Data Memory Advanced Topics 15-11 Advanced Topics and Other Information Describes the 8052 Assembly Language Syntax Label and instruction Number Bases Expressions Operator Precedence Characters and Character Strings−1.Order of Precedence for Mathematical Operators Order Operator Changing Program Flow LJMP, SJMP, Ajmp Ljmp LABEL3 Subroutines LCALL, ACALL, RET Register Assignment MOV MOV DestinationRegister,SourceValue MOV R2,R1 Invalid MOV @R0,A Incrementing and Decrementing Registers INC, DEC Program Loops Djnz Setting, Clearing, and Moving Bits SETB, CLR, CPL, MOV 16-14 Bit-Based Decisions and Branching JB, JBC, JNB, JC, JNC Value Comparison Cjne Lcall Debouncekey Less Than and Greater Than Comparison Cjne Checkless JC Aisless Zero and Non-Zero Decisions JZ/JNZ Performing Additions ADD, Addc Performing Additions ADD, Addc Performing Subtractions Subb Performing Multiplication MUL Performing Division DIV Shifting Bits RR, RRC, RL, RLC −1. Rotate Operations Bit-Wise Logical Instructions ANL, ORL, XRL −2.Results of ANL−3.Results of ORL −4.Results of XRL Assembly Language 16-25 Exchanging Register Values XCH Swapping Accumulator Nibbles Swap Adjusting Accumulator for BCD Addition DA Using the Stack PUSH/POP Assembly Language 16-29 Setting the Data Pointer Dptr MOV Dptr Reading and Writing External RAM/Data Memory Movx Reading Code Memory/Tables Movc Lcall SUB SUB INC a Using Jump Tables JMP @A+DPTR Describes the Keil simulator and its functions 17-2 Keil Simulator 17-3 Timers −1. Timer/Counter 0 − Mode Timer 0 & 1 Example −2. Timer/Counter −4. Timer/Counter 1 Mode Keil Simulator 17-7 17-8 Keil Simulator 17-9 17-10 −1.Timer/Counter 2 Control Bits TimerRegister Bit Toggle Box Name −7. Status of Watchdog Peripheral Watchdog Reset Facility Example 17-14 Keil Simulator 17-15 System Timer Clock Control Analog-to-Digital Converter −8. Analog−to−Digital Converter Peripheral −9. Error Message Summation/Shifter −10. Accumulator/Shifter Peripheral 17.8.1 ADC/Summation/Shifter Example 17-22 Keil Simulator 17-23 17-24 Keil Simulator 17-25 17-26 Keil Simulator 17-27 −11. summation/Shifter Peripheral Keil Simulator 17-29 −13. List Box for the Interrupt Peripheral −14. Parallel Port 0 Contents Display Window Ports Serial Peripheral Interface SPI −16. SPI Peripheral Window Keil Simulator 17-33 SPI Sample Code Keil Simulator 17-35 Serial Peripheral Interface SPI Keil Simulator 17-37 17.12 ∝Vision 2 Debug Program Example −17. Keil Debugger Serial Port I/O −18. Serial Channel 0 Communication Peripheral 17-42 BaudRate + fOSC Transmit Block Baud Rate ComputationBaudRate + fOSC @ Receive Block Baud Rate Computation −19. Clock Control Peripheral Additional Resource Appendix a Topic Additional Features in the MSC1210 Compared to Appendix B MSC1210 Timing Chain and Clock Control Diagram Figure B−1. MSC1210 Timing Chain and Clock Control Appendix C Table C−1. Boot ROM Routines Address Routine Declarations Description Boot ROM Routines Page Appendix D 8052 Instruction-Set Quick-Reference Guide JB bitAddr,relAddr Ajmp pg1Addr Appendix E Description Instruction Set Description 8052 Instruction Set AcallAbsolute Call within 2k Block Acall codeAddress Add Value, Add Value with Carry ADD, AddcADD A,operand Absolute Jump within 2k Block AjmpAjmp codeAddress Bitwise ANLANL operand1,operand2 Compare and Jump if Not Equal CLRClear Register Cjne operand1,operand2,reladdr Decimal Adjust Accumulator CPLComplement Register CPL operand Decrementing the value causes it to reset to 255 0xFFH Carry flag is not set when the value rolls over from 0 toDEC register See also INC, Subb Decrement and Jump if Not Zero Djnz register,relAddr Increment Reister INCINC register Jump if Bit Set JBCJump if Bit Set and Clear Bit Jump if Carry Set JNB JMPJNC Lcall JNZLjmp Not affected See also MOVC, MOVX, XCH, XCHD, PUSH, POP MOV operand1, operand2MOV bit1,bit2 Move into/out of Internal RAM MOVMOV operand1,operand2 Movc MOV DptrMovx MUL Multiply Accumulator by BNOP No Operation Bitwise or ORLSyntax ORL operand1,operand2 POP Pop Value from StackPush Push Value onto Stack RET Return from SubroutineReti Return from Interrupt RRC RLCSetb Sjmp Short JumpSubb Subtract from Accumulator with Borrow XCH SwapXchd XRL Bitwise Exclusive or Undefined Instructions OpCode Bytes Cycles Flags ??? 0xA5 Appendix F Enable Interrupt Control Eicon Extended Interrupt Enable EIEEX2-External 2 Interrupt Enable Bit Addressable SFRs alphabetical Interrupt Enable IE Extended Interrupt Priority EIP Interrupt Priority IP Port 0 P0 Port 1 P1 Port 2 P2 Port 3 P3 Program Status Word PSW Register Bank Register Bank Addresses Serial Mode Description Baud Serial Control Scon Timer Control Tcon Tcon Timer 2 Control T2CON T2CON Appendix G SFR/Address Cross-Reference SFR Name Description SFR Address Hex SFRs/Address Cross-Reference Guide alphabetical Spircon