Receive Serial Data Timing | Jameco Electronics 3000, 2000 manual

12.5 Receive Serial Data Timing

When the receiver is ready to receive data, a falling edge indicates that a start bit must be detected. The falling edge is detected as a different Rx input between two different clocks, the clock being 8x or 16x the baud rate. Once the start bit has been detected, data bits are sampled at the middle of each data bit and are shifted into the receive shift register. After 7 or 8 data bits have been received, the next bit will be either a 9th (8th) address bit, or a stop bit will be sampled. If the Rx line is low, it is an address bit and the address bit received bit in the status register will be enabled. If an address bit is detected, the receiver will attempt to sample the stop bit. If the line is high when sampled, it is a stop bit and a new scan for a new start bit will begin after the sample point. At the same time, the data bits are transferred into the receive data register and an interrupt, if enabled, is requested.

On receive, an interrupt is requested when the receiver data register has data. This hap- pens when data bits are transferred from the receive shift register to the data register. This also sets bit 7 of the status register. The interrupt request and bit 7 are cleared when the data register is read.

An interrupt is requested if bit 7 is high. The interrupt is requested on the edge of the transmitter data register becoming empty or the transmitter shift register becoming empty. The transmitter interrupt is cleared by writing to the status register or to the data register.

On receive, the scan for the next start bit starts immediately after the stop bit is detected. The stop bit is normally detected at a sample clock that nominally occurs in the center of the stop bit. If there is a 9th (8th) address bit, the stop bit follows that bit.

The serial clock can be configured to be either 16× the data rate or 8× the data rate.

		Serial Port
		Input Clock
	8 clocks
start bit	sampling		stop bit
	sampling
	point	Receiver Data
	point	Receiver Data
		Ready Bit
		Asynchronous Receive
		Transmitter Data Reg Full
		Asynchronous Transmit

Figure 12-4. Serial Port Synchronization

User’s Manual

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Image 190

Jameco Electronics 3000, 2000 manual Receive Serial Data Timing, Serial Port Synchronization

Contents

Page Rabbit 3000 Microprocessor Trademarks Rabbit Semiconductor Table of Contents Rabbit Internal I/O Registers Parallel Ports 129 Rabbit 3000 Clocks 209 Appendix B. Rabbit 3000 Revisions 273 Rabbit 3000 Microprocessor Introduction Features and Specifications Rabbit User’s Manual 1shows a block diagram of the Rabbit CPU Summary of Rabbit 3000 Advantages Feature Rabbit Differences Rabbit 3000 vs. Rabbit Serial ports with support for SDLC/HDLC IrDA Rabbit 3000 Design Features Rabbit 8-bit Processor vs. Other Processors 1 5 V Tolerant Inputs Overview of On-Chip Peripherals and FeaturesSerial Ports System Clock 4 32.768 kHz Oscillator Input Parallel I/O Cascaded Output Registers for Parallel Ports D and E Slave Port Rabbit Timers Auxiliary I/O Bus Input Capture Channels PWM Quadrature Encoder Inputs Pulse Width Modulation Outputs Spread Spectrum Clock Separate Core and I/O Power PinsDesign Standards Programming Port Standard Bios Dynamic C Support for the Rabbit Rabbit 3000 Microprocessor Details on Rabbit Microprocessor Features Processor Registers Rabbit 3000 Microprocessor Memory Mapping Addressing Memory Components Example of Memory Mapping Operation 4shows a memory interface unit Extended Code Space Separate I and D Space Extending Data Memory Use of XPC Segment Xpc window stack Using the Stack Segment for Data Storage Practical Memory Considerations Data RAM Root Code User’s Manual Instruction Set Outline Load Immediate Data to a Register Load or Store Data from or to a Constant Address Load or Store Data Using an Index Register Other 8-bit loads and stores are the following Register-to-Register Move Register Exchanges Push and Pop Instructions 7 16-bit Arithmetic and Logical Ops Bool SBC instruction can also be used to perform a sign extension Input/Output Instructions Exchanges Not Directly Implemented How to Do It in Assembly Language-Tips and TricksZero HL in 4 Clocks Manipulation of Boolean Variables Comparisons of Integers HLB Atomic Moves from Memory to I/O Space Interrupt Structure Interrupt Priority Effect of Processor Priorities on Interrupts Processor Priority Effect on Interrupts Multiple External Interrupting Devices Privileged Instructions, Critical Sections and Semaphores Semaphores Using Bit B,HL Critical Sections Computed Long Calls and Jumps Rabbit Capabilities Precisely Timed Output Pulses Pulse Width Modulation to Reduce Relay Power Using Open-Drain Outputs for Key Scan Open-Drain Outputs Used for Key Scan Cold Boot Slave Port Slave Rabbit As a Protocol Uart PIN Assignments and Functions Lqfp Package Pinout Mechanical Dimensions and Land Pattern Same pin dimensions apply along the x axis and the y axis PC Board Land Pattern for Rabbit 3000 128-pin Lqfp C D E F G H J K L M Ball Grid Array Package Key Feature Recommendation Ball and Land Size DimensionsDesign Considerations All dimensions in mm Nominal Ball Tolerance Ball Pitch Nominal Land BGA Package Outline Pin Pin Group Pin Name Direction Function Numbers Rabbit Pin DescriptionsRabbit Pin Descriptions Lqfp Tfbga Vddcore Bus Timing Bus Timing Read and Write Description of Pins with Alternate Functions Pins With Alternate Functions PF7 PWM3 AQD2A Parallel Port x Alternate Functions Parallel Port x Alternate Functions Control Bits Symbol Parameter Maximum Rating DC Characteristics3 Volt DC Characteristics Symbol Parameter Test Conditions Min Typ Max Units I/O Buffer Sourcing and Sinking Limit Rabbit 3000 Microprocessor Rabbit Internal I/O Registers Rabbit 3000 Peripherals and Interrupt Service Vectors On-Chip Peripheral ISR Starting Address Register Name Mnemonic Address Reset Default Values for all the Peripheral Control RegistersRabbit Internal I/O Registers Grev PEB7R PWM0R Tbcsr Sdar Miscellaneous Functions Global ROM Configuration RegisterGlobal RAM Configuration Register Processor Identification Global Revision Register Rabbit Oscillators and ClocksGlobal CPU Register Gcpu Rabbit Global Control/Status Register Global Control/Status RegisterClock Select Field of Gcsr Gcsr Global Clock Double Register Recommended Delays Set In Gcdr for Clock DoublerClock Doubler Gcdr Effect of Clock Doubler User’s Manual Clock Spectrum Spreader Reduction in Peak Spectral Strength from Spectrum Spreader Chip Select Options for Low Power Global Power Save Control Register Address = 0x0D Short Chip Select Memory Read Output Pins CLK, STATUS, /WDTOUT, /BUFEN Global Output Control Register Gocr = 0x0E Time/Date Clock Real-Time Clock 10. Real-Time Clock RTCxR Data Registers 11. Real-Time Clock Control Register Rtccr adr = Watchdog Timer 12. Watchdog Timer Control Register Wdtcr adr = 13. Watchdog Timer Test Register Wdttr adr = System Reset 14. Rabbit 3000 Reset Sequence and State of I/O Pins Pin Name Direction Reset Low Post-Reset† Recognized by CPU Rabbit Interrupt Structure 15. Interrupts-Priority and Action to Clear Requests External Interrupts External Interrupt Line Logic 16. Control Registers for External Interrupts Interrupt Vectors INT0 EIR,0x00/INT1 EIR,0x08Reg Name Reg Address Bits 7,6 Bits 5,4 Bits 3,2 Bits 1,0 Bootstrap Operation 102 Rabbit 3000 Microprocessor Pulse Width Modulator Pulse Width LSBs 1st 2nd 3rd 4th 17. PWM LSB x Register 18. PWM MSB x Register Input Capture 106 Rabbit 3000 Microprocessor Input Capture Control/Status Register 19. Input Capture Control/Status RegisterIccsr Iccr 20. Input Capture Control Register21. Input Capture Trigger x Register ICT1R 23. Input Capture LSB x Register 22. Input Capture Source x Register24. Input Capture MSB x Register Quadrature Decoder Rejected Quad Decode Control/Status Register 25. Quadrature Decoder Control/Status RegisterQdcsr Qdcr 26. Quadrature Decoder Control Register27. Quadrature Decoder Count Register QDC1R 114 Rabbit 3000 Microprocessor Memory Interface and Mapping Interface for Static Memory Chips Data Lines Static Address Lines Memory Flash RabbitRAM Memory-Mapping Unit Memory Mapping OverviewProcessor Memory Mapping Unit Interface Memory Chips Segment Size Register 64KSegment Registers Segment Register Function Memory Interface Unit Memory Bank Control Registers Memory Bank Control Register x MBxCR = 0x014 + MMU Instruction/Data Register Optional A16, A19 Inversions by Segment /CS1 EnableMMU Instruction/Data Register Mmidr = Mmidr Mecr Memory Timing Control Register MTCR, adr =MMU Expanded Code Register Memory Timing Control Register Breakpoint/Debug Control Register Allocation of Extended Code and DataBreakpoint/Debug Control Register BDCR, adr = 0x01C Bdcr Instruction and Data Space Support RAM Use of Physical Memory Separate I & D Space Model How the Compiler Compiles to Memory 128 Rabbit 3000 Microprocessor Parallel Ports Parallel Port a Registers Parallel Port aParallel Port a Data Register Bit Functions Parallel Port B Registers Parallel Port BParallel Port B Register Bit Functions Parallel Port C Registers Parallel Port CParallel Port C Register Bit Functions Parallel Port D Parallel Port D Registers PD7 Parallel Port D Control Register adr = Parallel Port D Register functionsBits 7 Bits 5 Bits 3 Bits 1 136 Rabbit 3000 Microprocessor Parallel Port E PE0 10. Parallel Port E Registers 11. Parallel Port E Register functions 12. Parallel Port E Control Register adr = 13. Parallel Port F Registers Parallel Port F14. Parallel Port F Register Functions Using Parallel Port a and Parallel Port F 15. Parallel Port F Control Register adr = 0x03C Summary Parallel Port a Parallel Port F 16. Parallel Port G Registers Parallel Port G17. Parallel Port G Data Register Functions Parallel Port G Control Register adr= 0x04C Read data Read strobe Chip select strobe 10. I/O Bank Control RegistersWrite data Write strobe T1 Tw T2 External I/O Timing with 1 wait state I/O Bank x Control Register External I/O Register Address Range and Pin Mapping Control Register Port E Address Pin A1513 Range 148 Rabbit 3000 Microprocessor Timers Timer a Reload Register Operation Timer a I/O Registers Timer a I/O Registers Timer a Control and Status Register Timer a CapabilitiesTacsr User’s Manual 153 Tacr Timer a Control RegisterTimer a Prescale Register Tapr Practical Use of Timer a Timer B Registers Timer BRegister Name Mnemonic Reset Address Tbcsr Timer B Control and Status RegisterTimer B Control Register Tbcr 11. Timer B Count MSB Register Timer B Count MSB x Registers10. Timer B Count LSB x Registers 12. Timer B Count LSB Register Using Timer B 160 Rabbit 3000 Microprocessor Serial Port Signal Name Function Serial Port SignalsRabbit Serial Ports Clka User’s Manual 163 Signals Shown at Microprocessor Tx Pin Serial Port Register Layout User’s Manual 165 Serial Port B Registers Serial Port RegistersSerial Port a Registers Serial Port C Registers Serial Port E Registers Serial Port D RegistersSerial Port F Registers Data Register All Ports Address Register All Ports 10. Long Stop Register All Ports 11. Status Register Asynchronous Mode Only All Ports Bits Value Description Clocked serial mode only 12. Status Register Clocked Serial Ports A-D only 13. Status Register Hdlc Mode Ports E and F only Bits Value Description Hdlc mode only Sacr 14. Serial Port Control Register Ports a and BSbcr Address = 0xE4 15. Serial Port Control Register Ports C and DSccr Sdcr Address = 0xCC 16. Serial Port Control Register Ports E and FSecr Sfcr 17. Extended Register Asynchronous Mode All Ports 18. Extended Register Clocked Serial Mode Ports A-D only 19. Extended Register Hdlc Mode Ports E and F only Serial Port Interrupt Transmitter IRQ Transmit Serial Data Timing Receive Serial Data Timing Serial Port Synchronization Clock Polarities Supported in Clocked Serial Mode Clocked Serial Ports User’s Manual 183 184 Rabbit 3000 Microprocessor Clocked Serial Timing With Internal Clock Clocked Serial TimingClocked Serial Timing with External Clock Valid Synchronous Communications on Ports E and F Last Byte Bit Pattern Valid Data Hits User’s Manual 189 190 Rabbit 3000 Microprocessor User’s Manual 191 Serial Port Software Suggestions Push AF IOI LD A,SCSR Controlling an RS-485 Driver and Receiver Transmitting Dummy Characters Using a Serial Port to Generate a Periodic Interrupt Transmitting and Detecting a Break Stop bit Start bit Data bits 9th bit low Parity, Extra Stop Bits with 7-Data-Bit CharactersParity, Extra Stop Bits with 8-Data-Bit Characters Stop bit Rabbit-Only Master/Slave Protocol Supporting 9th Bit Communication ProtocolsData Framing/Modbus User’s Manual 197 198 Rabbit 3000 Microprocessor Rabbit Slave Port SRD SCS Slave Port Read Cycle Symbol Parameter Minimum Maximum Following table explains the parameters used in Figure Slaveattn PB7 Typical Connection Slave Rabbit to Master Rabbit Slave Port Registers Hardware Design of Slave Port InterconnectionSlave Port Registers Register Mnemonic Internal Address External Address Slave Port Control Register Spcr adr = Bit Bits 6,5 Bit 3,2 Bits 1,0 Write Only Read Only Slave Applications Applications and Communications Protocols for SlavesSlave Port Status Register Spsr adr = Master-Slave Messaging Protocol 208 Rabbit 3000 Microprocessor Rabbit 3000 Clocks Rabbit 3000 Main Oscillator Circuit Low-Power Design EMI Control Power Supply Connections and Board Layout Using the Clock Spectrum Spreader GCM0R Spread Spectrum Enable/Disable RegisterSpread Spectrum Mode Select GCM1R 214 Rabbit 3000 Microprocessor Access Enable Access MHz AC Timing SpecificationsMemory Access Time Memory Requirements at 3.3 V, -40C to +85C, Adr Bus 60 pF VDD Data and Clock Delays VDD ±10%, Temp, -40C-+85C maximumNormal Strong 30 pF 60 pF 90 pF No dbl/dbl CSx Memory Write Time Delays Memory Read Time DelaysTime Delay Output Capacitance 30 pF 60 pF 90 pF CLK A190 CSx WEx D70 Example Clock Doubler Max-Min Clock Low Times 222 Rabbit 3000 Microprocessor 16.2 I/O Access Time Bufen I/O Read Time Delays I/O Write Time Delays Further Discussion of Bus and Clock Timing Clock Doubler and Memory Timing Conditions Commercial Ratings Industrial Ratings Maximum Clock SpeedsMaximum Clock Speeds at 3.3 V Preliminary Period Frequency External Oscillator Buffer Power and Current Consumption User’s Manual 229 Rabbit 3000 System Current vs. Frequency at 3.3 11. Sleepy Mode Current Consumption Current Consumption Mechanisms Sleepy Mode Current Consumption Memory Current Consumption Battery-Backed Clock Current Consumption Current is negligible for V 1.14 Reduced-Power External Main Oscillator Voltage Current incl built-in buffer Bios Rabbit Bios and Virtual DriverBios Services Virtual Driver Bios AssumptionsWatchdog Timer Support Periodic Interrupt User’s Manual 239 240 Rabbit 3000 Microprocessor Power Management Support Other Rabbit Software Using Library Functions Using Assembly LanguageReading and Writing I/O Registers Interrupt While Updating Registers Shadow RegistersUpdating Shadow Registers Atomic Instruction Write-only Registers Without Shadow Registers Timer and Clock UsageNon-atomic Instructions Format of the structure used is the following 246 Rabbit 3000 Microprocessor Rabbit Instructions Summary Spreadsheet Conventions Flag Description Symbols Rabbit Z180 Meaning 19.3 8-bit Indexed Load and Store Load Immediate DataLoad & Store to Immediate Address 19.4 16-bit Indexed Loads and Stores 19.5 16-bit Load and Store 20-bit Address Register to Register Moves Stack Manipulation Instructions Exchange Instructions19.9 16-bit Arithmetic and Logical Ops 19.10 8-bit Arithmetic and Logical Ops ADD A,HL 19.11 8-bit Bit Set, Reset and Test 19.12 8-bit Increment and Decrement 19.13 8-bit Fast a Register Operations 19.14 8-bit Shifts and Rotates Instruction Prefixes Block Move Instructions Control Instructions Jumps and Calls Miscellaneous Instructions Privileged Instructions Following instructions are privileged Differences Rabbit VS. Z80/Z180 Instructions Z80/Z180 Instructions Dropped Rabbit Instructions to Use IOI and IOE I Column Symbol Key Flag Register Key Rabbit Z180 Meaning Z V C EX AF,AF LD A,BC LDP HL,IX RRA 268 Rabbit 3000 Microprocessor Appendix A. the Rabbit Programming Port Programming Port PIN Assignments Use of the Programming Port as a Diagnostic/Setup Port Alternate Programming Port Suggested Rabbit Crystal Frequencies Non-Stock Crystals Appendix B. Rabbit 3000 Revisions 274 Rabbit 3000 Microprocessor User’s Manual 275 Rabbit Description 3000 3000A Discussion of Fixes and ImprovementsTable B-1. Summary of Rabbit 3000 Improvements and Fixes IL1T/IZ1T IL2T/IZ2T Table B-2. Reset State of New Rabbit 3000A I/O Registers Rabbit Internal I/O Registers Iuer Rabbit Register Name Mnemonic 3000 3000A Address Reset Peripheral and ISR Address On-Chip Peripheral Address Range ISR Starting Address User’s Manual 281 Processor Revision Package Revision-Level ID RegisterTable B-5. Rabbit 3000 Revision Identification Information Gcpu Grev System/User Mode Write Protect Control Register Memory ProtectionTable B-6. Write Protect Control Register Wpcr Write Protect Low Register Table B-7. Write Protect Low RegisterWplr Wphr Table B-8. Write Protect High RegisterTable B-9. Write Protect Segment x Register Wpsar Wpsalr Table B-10. Write Protect Segment x Low RegisterWrite Protect Segment x Low Register Wpsblr Wpsahr Table B-11. Write Protect Segment x High RegisterWrite Protect Segment x High Register Wpsbhr Stack Protection Figure B-2. Simple Stack Protection Layout Table B-13. Stack Low Limit Register Table B-12. Stack Limit Control RegisterTable B-14. Stack High Limit Register RAM Segment Register RAM Segment RelocationTable B-15. RAM Segment Register Ramsr Table B-17. Secondary Watchdog Timer Register Secondary Watchdog TimerTable B-16. Watchdog Timer Control Register-Updated Wdtcr Instruction Bytes Clks Operation New OpcodesTable B-18. New Rabbit 3000 Opcodes New UMA/UMS Opcodes Source Destination Table B-19. Rabbit 3000 Revision Block Copy Opcode EffectsNew Block Copy Opcodes IOI/IOE Expanded I/O Memory Addressing Table B-20. MMU Instruction/Data Register External I/O Improvements Table B-21 Bank x Control Register Short Chip Select Timing for Writes Table B-22. Global Power Save Control RegisterAddress = 0x000D Table B-23. Global Control/Status Register Clock Select and Power Save ModesTable B-24. Clock Select Field of Gcsr Short Chip Select Timing Figure B-3. Short Chip Select Timing CLK/8, Read Operation Figure B-4. Short Chip Select Timing CLK/6, Read Operation Figure B-6. Short Chip Select Timing CLK/2, Read Operation Figure B-7. Short Chip Select Timing 2 kHz, Read Operation Figure B-9. Short Chip Select Timing 8 kHz, Read Operation Figure B-11. Short Chip Select Timing 32 kHz, Read Operation Figure B-12. Short Chip Select Timing CLK/8, Write Operation Figure B-13. Short Chip Select Timing CLK/6, Write Operation Figure B-15. Short Chip Select Timing CLK/2, Write Operation Figure B-16. Short Chip Select Timing 2 kHz, Write Operation Figure B-18. Short Chip Select Timing 8 kHz, Write Operation 310 Rabbit 3000 Microprocessor Pulse Width Modulator Improvements Figure B-21. PWM Interrupt and Output Timing PWM LSB 0 Register Table B-25. PWM LSB 0 RegisterTable B-26. PWM LSB 1 Register PWM LSB 1 Register Address = 0x008C Table B-27. PWM LSB 2 and 3 RegistersAddress = 0x008E Table B-29. Quadrature Decoder Count High Register Quadrature Decoder ImprovementsTable B-28. Quadrature Decoder Control Register QDC1HR User’s Manual 315 Pins with Alternate Functions Serial Ports E/F System Mode User Mode Appendix C. SYSTEM/USER ModeTable C-1. Differences Between System and User Modes Table C-2. New System/User Mode Opcodes System/User Mode OpcodesInstruction Bytes Clk Operation Priv System/User Mode Registers Table C-3. System/User Mode I/O Registers Table C-4. I/O Addresses Inaccessible in User Mode Register Name Mnemonic Address Figure C-1. Interrupt Handing in System/User Mode Interrupts Peripheral Interrupt Prioritization Table C-5. Interrupts-Priority and Action to Clear Requests Using the System/User Mode Memory Protection Only Mixed System/User Mode Operation Figure C-3. System/User Mode Setup for Mixed Operation Figure C-4. System/User Mode Setup for Operating System Complete Operating System Appendix D. Rabbit 3000A Internal I/O Registers Table D-1 Rabbit 3000A Internal I/O Registers Table D-1. Rabbit 3000A Internal I/O Registers 0x03C0 00000000 Serial Port E User Enable Register 0x006A Xxxxxxxx Port D Bit 3 Register 0x0082 00000000 Bank 3 Control Register 0x0098 Xx000000 Interrupt 1 Control Register 0x00D1 Xxxxxxxx Serial Port B Long Stop Register 334 Rabbit 3000 Microprocessor User’s Manual 335 Page Index Numerics Memory A16, A19 inversions /CS1 PWL2R, PWL3R 200