Using Jump Tables JMP @A+DPTR | Texas Instruments MSC1210 specs

Using Jump Tables (JMP @A+DPTR)

16.31 Using Jump Tables (JMP @A+DPTR)

A frequent method for quickly branching to many different areas in a program is by using jump tables. For example, branching to different subroutines based on the value of the accumulator could be accomplished with the CJNE instruc- tion (which has already been covered):

CJNE	A,#00h,CHECK1 ;If		it’s		not zero, jump to CHECK1
AJMP	SUB0	;Go	to	SUB0		subroutine
CHECK1: CJNE	A,#01h,CHECK2 ;If it’s				not 1, jump to CHECK2
AJMP	SUB1	;Go	to	SUB1		subroutine
CHECK2:

This code will work, but each additional possible value increases the size of the program by 5 bytes—3 bytes for the CJNE instruction and 2 bytes for the AJMP instruction.

A more efficient way is to create a jump table by using the JMP @A+DPTR instruction. Like the MOVC @A+DPTR, this instruction calculates an address by summing the accumulator and DPTR, and then jumps to that address. Therefore, if DPTR holds 2000H and the accumulator holds 14H, the JMP instruction jumps to 2014H.

Consider the following code:

RL A	;Rotate accumulator left, multiply by 2
MOV DPTR,#JUMP_TABLE	;Load DPTR with address of jump table
JMP @A+DPTR	;Jump to the corresponding address
JUMP_TABLE: AJMP SUB0	;Jump table entry to SUB0
AJMP SUB1

This code first takes the value of the accumulator and multiplies it by two by shift- ing the accumulator to the left by one bit. The accumulator must first be multiplied by two because each AJMP entry in JUMP_TABLE is two bytes long,

The code then loads the DPTR with the address of the JUMP_TABLE and pro- ceeds to JMP to the address of the accumulator plus DPTR. No additional checks are necessary because we already know that we want to jump to the offset indicated by the accumulator. We jump directly into the table that jumps to our subroutine. Each additional entry in the jump table will require only two additional bytes (two bytes for each AJMP instruction).

Note:

It is almost always a good idea to use a jump table if there are two or more choices based on a zero-based index. A jump table with just two entries, like the previous example, saves one byte of memory over using the CJNE ap- proach, and saves three bytes of memory for each additional entry.

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Texas Instruments MSC1210 manual Using Jump Tables JMP @A+DPTR

Contents

User’s Guide Important Notice Introduction to the MSC1210 MSC1210 Memory OrganizationBasic Registers Addressing Modes System TimingSerial 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 Reset Line RST Address Latch Enable ALEProgram Store Enable Psen External Access EA Enhanced 8051 Core −3. MSC1210 Timing Compared to Standard 8051 Timing Family Device Compatibility Flash MemoryHigh 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 Data Memory −2. Program and Data Memory AddressesOn-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 Mode Example Immediate Addressing−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 Direct Calls Returns From RoutinesInterrupts 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 Normal-Mode Power-On Reset Timing Flash Programming Mode Power-On Reset TimingStartup Timing Symbol Parameter Min Max Unit Psen Describes the timers of the MSC1210 ADC How Does a Timer Count? Using Timers to Measure TimeHow Long Does a Timer Take to Count? RD or WR Strobe Width Width ∝sMovx Duration SYS CLKs At 12MHz Timer SFRs −1. Timer Conrol SFRsSFR Name Description SFR Address Bit Addressable? Tmod SFR Mode −2. Timer Modes and Usage TxM1 TxM0 Timer Description of Timer Mode −3. Example of 8-Bit Auto-Reload InstructionCycle Bit Name Bit Address Explanation of Function Timer Tcon SFR−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 −6. Baud Rate Settings for Timer Writing to the Serial PortBaud Rate 33MHz clk 25MHz clk 11.0592MHz clk Kb/s Reading the Serial Port Describes the interrupts of the MSC1210 ADC JNB TF0,SKIPTOGGLE Interrupt/Event Addr Priority Flag Enable Priority Control Events That Can Trigger Interrupts−1.Interrupt Sources 10-4 Enabling Interrupts −2.IE A8 H SFR−3.EICON D8 H SFR −4.EIE E8 H SFR Polling Sequence Interrupt Priorities −5.IP B8 H SFR−6.EIP F8 H SFR Interrupt Triggering Exiting Interrupts Types of Interrupts Serial InterruptsExternal Interrupts −7.EXIF 91 H SFR Bit Name Explanation of Function Timer Interrupts Watchdog InterruptAuxiliary Interrupts −8.Clearing Auxiliary Interrupts −9.AIE A6 H SFRAux Interrupt Type Method to Clear Interrupt −10. Aistat A7 H SFR −11. PAI A5 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 Description 11-2 Tone Generator 11-3PWM 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 −4. Configuring the PWM for Tone Generation with PWM Idling −5. Statement ExplanationsExplanation 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 −2.Calibration Mode Control Bits Calibration ModeCalibration 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 Watchdog Timer 14-4 Description 14-2Low-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 Updating Interrupts with Reset Sector Lock Advanced Flash MemoryWrite 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 Timer −1.Timer/Counter 2 Control BitsRegister 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 Transmit Block Baud Rate Computation BaudRate + fOSCBaudRate + 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, Addc Add Value, Add Value with CarryADD A,operand Ajmp Absolute Jump within 2k BlockAjmp codeAddress ANL BitwiseANL 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 INC Increment ReisterINC register Jump if Bit Set JBCJump if Bit Set and Clear Bit Jump if Carry Set JMP JNBJNC JNZ LcallLjmp MOV operand1, operand2 Not affected See also MOVC, MOVX, XCH, XCHD, PUSH, POPMOV bit1,bit2 MOV Move into/out of Internal RAMMOV operand1,operand2 MOV Dptr MovcMovx MUL Multiply Accumulator by BNOP No Operation ORL Bitwise orSyntax ORL operand1,operand2 POP Pop Value from StackPush Push Value onto Stack RET Return from SubroutineReti Return from Interrupt RLC RRCSetb Sjmp Short JumpSubb Subtract from Accumulator with Borrow Swap XCHXchd 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