Timer 2 as a Baud Rate Generator | Texas Instruments MSC1210

Using Timer 2

8.5.4Timer 2 as a Baud Rate Generator

Timer 2 can be used as a baud rate generator. This is accomplished by setting either RCLK (T2CON.5) or TCLK (T2CON.4).

With Timer 1, the receive and transmit baud rate must be the same. With Timer 2, however, the user can configure the serial port to receive at one baud rate and transmit at another. For example, if RCLK is set and TCLK is cleared, seri- al data is received at the baud rate determined by Timer 2, whereas the baud rate of transmitted data is determined by Timer 1.

Determining the auto-reload values for a specific baud rate is discussed in Chapter 9, Serial Communication. The only difference is that in the case of Timer 2, the auto-reload value is placed in RCAP2H and RCAP2L, and the val- ue is 16-bit rather than 8-bit.

Note:

When Timer 2 is used as a baud rate generator (either TCLK or RCLK are set), the Timer 2 overflow flag (TF2) is not set.

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Image 90

Texas Instruments MSC1210 manual Timer 2 as a Baud Rate Generator

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 Boot ROM Routines Additional Features in the MSC1210 Compared toClock Timing Diagram 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 BaudRate + Timer2Overflow −2. Common Baud Rates Using TimerBaudRate + 32 @ Timer1Overflow BaudRate + 12 @ 256 * TH1 Rcap 2H Rcap 2L + −3. Common Baud Rates Using TimerSerial Mode 2 Asynchronous Full-Duplex 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 TH1 = 256 − Crystal / 192 / Baud Setting the Serial Port Baud Rate−4. Mode 0 Commonly Used Baud Rates 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 −3.EICON D8 H SFR Enabling Interrupts−2.IE A8 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 Duty Cycle = PWM Period +1 − PWM Duty/PWM Period +1 PWM Generator−1. PWM Polarity Conditions Condition Duty Cycle −5. Timing Diagram of a PWM Waveform This can be expressed in code as Example of PWM Tone Generation −2. Configuring the PWM for Tone GenerationStmt ‘C’ Source Code Assembly Source Code −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 @ 10 Input BufferAnalog Input 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 −4.Output Data Rate and Channel Rate Multiplexing Channels−3.Filter Settling 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 PT100 Ratiometric MeasurementsADC Result + V REF ADC Result + R REF @ I OUT Differential Vref 12-26 SPI System Errors 13-6 Clock Phase and Polarity Controls 13-4SPI Signals 13-5 Description 13-2 −1. SPI block diagram Functional Description −2. SPI Clock/Data Timing Clock Phase and Polarity Controls Master Out Slave SPI SignalsMaster In Slave Out 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 −1.Typical Sub-Circuit Current Consumption Power Supply−2.Comparator Specification −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 Advanced Flash Memory 15-6 Hardware Configuration 15-2Power Optimization 15-9 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 −1.Order of Precedence for Mathematical Operators Operator PrecedenceCharacters and Character Strings 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 −3.Results of ORL Bit-Wise Logical Instructions ANL, ORL, XRL−2.Results of ANL −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 Absolute Call within 2k Block 8052 Instruction SetAcall Acall codeAddress ADD, Addc Add Value, Add Value with CarryADD A,operand Ajmp Absolute Jump within 2k BlockAjmp codeAddress ANL BitwiseANL operand1,operand2 Clear Register Compare and Jump if Not EqualCLR Cjne operand1,operand2,reladdr Complement Register Decimal Adjust AccumulatorCPL CPL operand DEC register Decrementing the value causes it to reset to 255 0xFFHCarry flag is not set when the value rolls over from 0 to See also INC, Subb Decrement and Jump if Not Zero Djnz register,relAddr INC Increment ReisterINC register Jump if Bit Set and Clear Bit Jump if Bit SetJBC 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 NOP MULMultiply Accumulator by B No Operation ORL Bitwise orSyntax ORL operand1,operand2 Push POPPop Value from Stack Push Value onto Stack Reti RETReturn from Subroutine Return from Interrupt RLC RRCSetb Subb SjmpShort Jump Subtract from Accumulator with Borrow Swap XCHXchd XRL Bitwise Exclusive or Undefined Instructions OpCode Bytes Cycles Flags ??? 0xA5 Appendix F EX2-External 2 Interrupt Enable Enable Interrupt Control EiconExtended Interrupt Enable EIE 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