TI486 Microprocessor - Al Kossow's Bitsavers

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Interrupts and Exceptions 2.5.3 Interrupt Vectors When the CPU services an interrupt or exception, the current program's instruction pointer and flags are pushed onto the stack to allow resumption of execution of the interrupted program. In protected mode, the processor also saves an error code for some exceptions. Program control is then transferred to the interrupt handler (also called the interrupt service routine). Upon execution of an IRET at the end of the service routine, program execution resumes at the instruction pointer address saved on the stack when the interrupt was serviced. Interrupt Vector Assignments Table 2-19. Interrupt Vector Assignments Each interrupt (except 8MI) and exception is assigned one of 256 interrupt vector numbers (Table 2-19). The first 32 interrupt vector assignments are defined or reserved. INT instructions acting as software interrupts may use any of the interrupt vectors, 0 through 255. The non-maskable hardware interrupt (NMI) is assigned vector 2. In response to a maskable hardware interrupt (INTR), the TI486 issues interrupt acknowledge bus cycles used to read the vector number from external hardware. These vectors should be in the range 32-255 because vectors 0-31 are predefined. Note: INTERRUPT VECTOR FUNCTION 0 Divide error FAULT EXCEPTION TYPE 1 Debug exception TRAP (see Note) 2 NMI interrupt - 3 Breakpoint TRAP 4 Interrupt on overflow TRAP 5 BOUND range exceeded FAULT 6 Invalid opcode FAULT 7 Device not available FAULT 8 Double fault ABORT 9 Coprocessor segment overrun ABORT 10 InvalidTSS FAULT 11 Segment not present FAULT 12 Stack fault FAULT 13 General protection fault FAULT 14 Page fault FAULTffRAP 15 Reserved - 16 Coprocessor error FAULT 17 Alignment check exception FAULT 18-31 Reserved - 32-255 Maskable hardware interrupts TRAP 0-255 Programmed interrupt TRAP Some debug exceptions may report both traps on the previous instruction and faults on the next instruction. 2-47
Interrupts and Exceptions Interrupt Descriptor Table The interrupt vector number is used by the TI486 to locate an entry in the interrupt descriptor table (IDT). In real mode, each IDT entry consists of a four-byte far pointer to the beginning of the corresponding interrupt service routine. In protected mode, each IDT entry is an eight-byte descriptor. The Interrupt Descriptor Table Register (IDTR) specifies the beginning address and limit of the IDT. Following reset, the IDTR contains a base address of Oh with a limit of 3FFh. The IDT can be located anywhere in physical memory as determined by the IDTR register. The IDT may contain different types of descriptors: interrupt gates, trap gates, and task gates. Interrupt gates are used mainly to enter a hardware interrupt handler. Trap gates are generally used to enter an exception handler or software interrupt handler. If an interrupt gate is used, the Interrupt Enable Flag (IF) in the EFLAGS register is cleared before the interrupt handler is entered. Task gates are used to make the transition to a new task. 2.5.4 Interrupt and Exception Priorities As the TI486 executes instructions, it follows a consistent policy for prioritizing exceptions and hardware interrupts as listed in Table 2-20. SMM interrupts always take precedence. Debug traps for the previous instruction and next instruction are handled in the next priority. When NMI and maskable INTR interrupts are both detected at the same instruction boundary, the TI486 microprocessor services the NMI interrupt first. The TI486 checks for exceptions in parallel with instruction decoding and execution. Several exceptions can result in a single instruction. However, only one exception is generated upon each attempt to execute the instruction. Each exception service routine should make the appropriate corrections to the instruction and then restart the instruction. In that way, exceptions can be serviced until the instruction executes properly. The TI486 supports instruction restart after all faults, except when an instruction causes a task switch to a task whose task state segment (TSS) is partially not present. A TSS can be partially not present if the TSS is not page aligned and one of the pages (where the TSS resides) is not currently in memory. 2-48 Programming Interface
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.TEXAS INSTRUMENTS TI486 Microproce
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TI486 Microprocessor Reference Guid
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Preface Read This First About This
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About This Manual Appendix D Orderi
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Contents 1 Product Overview .......
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Contents 5.5 AC Characteristics . .
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1-1 TI486SLC/E Functional Block Dia
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Figures 4-27 SUSP Initiated Suspend
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Tables 5-3 Absolute Maximum Ratings
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Product Overview 1-1
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Chapter 1 Product Overview Features
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1.2 Differences Between the TI486SL
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Tl486SLCIE Overview Figure 1-2. TI4
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Tl486DLCIE Overview 1.4 TI486DLC/E
Page 30 and 31: TI486DLCIE Overview The TI486DLC/E
Page 32 and 33: Power Management / System Managemen
Page 34 and 35: Programming Interface 2-1
Page 36 and 37: Chapter 2 In this chapter, the inte
Page 38 and 39: Processor Initialization Table 2-1.
Page 40 and 41: Instruction Set Overview 2.2 Instru
Page 42 and 43: Register Set 2.3 Register Set There
Page 44 and 45: Register Set Pointer and Index Regi
Page 46 and 47: Register Set 2.3.1.2 Segment Regist
Page 48 and 49: Register Set 2.3.1.3 Instruction Po
Page 50 and 51: Register Set 2.3.2 System Register
Page 52 and 53: Register Set 2.3.2.1 Control Regist
Page 54 and 55: Register Set 2.3.2.2 Descriptor Tab
Page 56 and 57: Register Set Table 2-6. Segment Des
Page 58 and 59: Register Set During task switching,
Page 60 and 61: Register Set The CCRO register (Tab
Page 62 and 63: Register Set Table 2-9. TI486DLCIE
Page 64 and 65: Register Set Table 2-12. ARR 1-ARR4
Page 66 and 67: Register Set 2.3.2.6 Test Registers
Page 68 and 69: Register Set Table 2-14. TR6 and TR
Page 70 and 71: Address Spaces 2.4 Address Spaces T
Page 72 and 73: Address Spaces 2.4.2 Memory Address
Page 74 and 75: Address Spaces Figure 2-21. Real Mo
Page 76 and 77: Address Spaces Figure 2-24. Paging
Page 78 and 79: Interrupts and Exceptions 2.5 Inter
Page 82 and 83: Interrupts and Exceptions Table 2-2
Page 84 and 85: System Management Mode 2.6 System M
Page 86 and 87: System Management Mode Figure 2-29.
Page 88 and 89: System Management Mode The new SMM
Page 90 and 91: System Management Mode During SMM o
Page 92 and 93: Protection The Current Privilege Le
Page 94 and 95: Virtual 8086 Mode 2.9 Virtual 8086
Page 96 and 97: TI486SLC/E Bus Interface 3-1
Page 98 and 99: Chapter 3 TI486SLC/E Bus Interface
Page 100 and 101: Overview Table 3-1. TI486SLCIE Sign
Page 102 and 103: Overview Table 3-2. Terminal Functi
Page 108 and 109: Overview 3.1.1 Bus Cycle Definition
Page 110 and 111: Overview Table 3-5 shows the state
Page 112 and 113: Functional Timing Figure 3-3. Bus A
Page 114 and 115: Functional Timing 3.2.2.1 Bus Cycle
Page 116 and 117: Functional Timing Non-Pipelined Wai
Page 118 and 119: Functional Timing Because of the de
Page 120 and 121: Functional Timing Pipelined Wait St
Page 122 and 123: Functional Timing Initiating and Ma
Page 124 and 125: Functional Timing Figure 3-12. Comp
Page 126 and 127: Functional Timing Figure 3-13. Inte
Page 128 and 129: Functional Timing Shutdown Indicati
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Functional Timing Figure 3-17. Pipe
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Functional Timing As shown in Figur
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Functional Timing Figure 3-19. Requ
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Functional Timing Figure 3-22. 8MI
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Functional Timing HALT Initiated Su
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Functional Timing 3.2.12 Float Figu
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TI486DLC/E Bus Interface 4-1
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Chapter 4 TI486DLC/E Bus Interface
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Overview Table 4-1. TI486DLCIE SIgn
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Overview Table 4-2. Terminal Functi
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Overview Table 4-6. Signal States D
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Overview 4.1.2 Power Management 4.1
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Functional Timing 4.2 Functional Ti
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Functional Timing The TI486DLC/E da
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Functional Timing Non-Pipelined Rea
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Functional Timing Initiating and Ma
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Functional Timing Figure 4-8. Faste
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Functional Timing Figure 4-9. Vario
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Functional Timing Once a pipelined
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Functional Timing 4.2.3 Bus Cycles
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Functional Timing Pipelined Cycles
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Functional Timing LOCK is activated
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Functional Timing 4.2.6 Halt and Sh
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Functional Timing Figure 4-17. Pipe
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Functional Timing Figure 4-19. Non-
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Functional Timing The TI486DLC/E sa
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Functional Timing 4.2.9 Hold Acknow
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Functional Timing 4.2.10 Coprocesso
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Functional Timing 4.2.12 Power Mana
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Functional Timing Stopping the Inpu
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Electrical Specifications 5-1
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Chapter 5 Electrical Specifications
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ElectricalConnecnons It is recommen
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Recommended Operating Conditions 5.
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DC Electrical Characteristics Table
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AC Characteristics Figure 5-2. TI48
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AC Characteristics Table 5-9. AC Ch
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AC Characteristics Table 5-11. AC C
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____ AC Characteristics 5.5.3 RESET
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Mechanical Specifications 6-1
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Chapter 6 Mechanical Specifications
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Pin Assignments Table 6-1. TI486SLC
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Pin Assignments Figure 6-3. TI486DL
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Package Dimensions 6.2 Package Dime
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Thermal Characteristics 6.3 Thermal
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Instruction Set 7-1
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Chapter 7 Instruction Set This sect
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Instruction Fields 7.2 Instruction
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Instruction Fields 7.2.5 reg Field
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Instruction Fields Table 7-7. mod r
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Instruction Fields 7.2.11 sreg3 Fie
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Clock Count Summary 7.4 Clock Count
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--- --;.J -L 01 Table 7-17. Instruc
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I . ~ -.....J Table 7-17. Instructi
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Table 7-17. Instructions, Opcodes,
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-....J N (J.) Table 7-17. Instructi
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I I i I i Table 7-17. Instructions,
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...... ...... '" Table 7-17. Instru
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-....J N co Table 7-17. Instruction
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"-.I ~ Table 7-17. Instructions, Op
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U Appendix A TI486 SMM Pro rammer's
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SMM Implementation A.2 SMM Implemen
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Figure A-1. SMM Memory Space Header
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SMM Implementation 6) NMI is the on
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Instruction Summary A.4 Instruction
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Instruction Summary A.4.3 Resume No
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Instruction Summary A.4.6 Save LDTR
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8MI Handler Example A.5 SMI Handler
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8MI Handler Example execute_halt: C
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8MI Handler Example COMMENT A The T
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8MI Handler Example arrl arr2 arr3
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.MODEL SMALL . STACK .386P INCLUDE
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Testing/Debugging SMM Code sgdt COM
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Testing/Debugging SMM Code i*******
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TI486 Power Management Features A.7
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Detection of Tl486 CPU A.9 Detectio
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Detection of SMM Capable Version A.
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A.11 SMM Feature Comparison SMM Fea
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SMM Instruction Macros COMMENT A Co
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SMM Instruction Macros SMM Instruct
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A.14 Format of Data Used by SVDC/RS
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Altering SMM Code Limits A.1S Alter
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SMM Errata A.16 SMM Errata The foll
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Appendix B TI486 Cache Flush B.1 Ge
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Appendix C TI486 BIOS Modification
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Introduction Some example assembler
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Appendix D Ordering Information 0.1
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~TEXAS INSTRUMENTS Printed in U.S.A
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TI486 Microprocessor - Al Kossow's Bitsavers

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