Motorola M68000 User manual

©MOTOROLA INC., 1993
M68000
8-/16-/32-Bit
Microprocessors User’s Manual
µ
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µ MOTOROLA
Ninth Edition
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MOTOROLA M68000 USER’S MANUAL vii
TABLE OF CONTENTS
Paragraph Page
Number Title Number
Section 1
Overview
1.1 MC68000.....................................................................................................1-1
1.2 MC68008.....................................................................................................1-2
1.3 MC68010.....................................................................................................1-2
1.4 MC68HC000................................................................................................1-2
1.5 MC68HC001................................................................................................1-3
1.6 MC68EC000................................................................................................1-3
Section 2
Introduction
2.1 Programmer's Model ................................................................................... 2-1
2.1.1 User's Programmer's Model .................................................................... 2-1
2.1.2 Supervisor Programmer's Model ............................................................. 2-2
2.1.3 Status Register........................................................................................ 2-3
2.2 Data Types and Addressing Modes ............................................................ 2-3
2.3 Data Organization In Registers................................................................... 2-5
2.3.1 Data Registers......................................................................................... 2-5
2.3.2 Address Registers ................................................................................... 2-6
2.4 Data Organization In Memory ..................................................................... 2-6
2.5 Instruction Set Summary............................................................................. 2-8
Section 3
Signal Description
3.1 Address Bus................................................................................................ 3-3
3.2 Data Bus...................................................................................................... 3-4
3.3 Asynchronous Bus Control.......................................................................... 3-4
3.4 Bus Arbitration Control ................................................................................ 3-5
3.5 Interrupt Control .......................................................................................... 3-6
3.6 System Control............................................................................................ 3-7
3.7 M6800 Peripheral Control ........................................................................... 3-8
3.8 Processor Function Codes.......................................................................... 3-8
3.9 Clock ........................................................................................................... 3-9
3.10 Power Supply.............................................................................................. 3-9
3.11 Signal Summary......................................................................................... 3-10
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viii M68000 USER’S MANUAL MOTOROLA
TABLE OF CONTENTS (Continued)
Paragraph Page
Number Title Number
Section 4
8-Bit Bus Operations
4.1 Data Transfer Operations.............................................................................4-1
4.1.1 Read Operations ......................................................................................4-1
4.1.2 Write Cycle ...............................................................................................4-3
4.1.3 Read-Modify-Write Cycle..........................................................................4-5
4.2 Other Bus Operations...............................................................................4-8
Section 5
16-Bit Bus Operations
5.1 Data Transfer Operations............................................................................5-1
5.1.1 Read Operations .....................................................................................5-1
5.1.2 Write Cycle .............................................................................................. 5-4
5.1.3 Read-Modify-Write Cycle.........................................................................5-7
5.1.4 CPU Space Cycle.................................................................................... 5-9
5.2 Bus Arbitration .......................................................................................... 5-11
5.2.1 Requesting The Bus..............................................................................5-14
5.2.2 Receiving The Bus Grant ...................................................................... 5-15
5.2.3 Acknowledgment of Mastership (3-Wire Arbitration Only).....................5-15
5.3 Bus Arbitration Control.............................................................................. 5-15
5.4 Bus Error and Halt Operation....................................................................5-23
5.4.1 Bus Error Operation .............................................................................. 5-24
5.4.2 Retrying The Bus Cycle.........................................................................5-26
5.4.3 Halt Operation ....................................................................................... 5-27
5.4.4 Double Bus Fault...................................................................................5-28
5.5 Reset Operation........................................................................................5-29
5.6 The Relationship of DTACK, BERR, and HALT .........................................5-30
5.7 Asynchronous Operation ..........................................................................5-32
5.8 Synchronous Operation ............................................................................5-35
Section 6
Exception Processing
6.1 Privilege Modes............................................................................................6-1
6.1.1 Supervisor Mode ......................................................................................6-2
6.1.2 User Mode................................................................................................6-2
6.1.3 Privilege Mode Changes ..........................................................................6-2
6.1.4 Reference Classification...........................................................................6-3
6.2 Exception Processing...................................................................................6-4
6.2.1 Exception Vectors ....................................................................................6-4
6.2.2 Kinds Of Exceptions.................................................................................6-5
6.2.3 Multiple Exceptions...................................................................................6-8
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MOTOROLA M68000 USER’S MANUAL ix
TABLE OF CONTENTS (Continued)
Paragraph Page
Number Title Number
Section 6
Exception Processing
6.2.4 Exception Stack Frames.......................................................................... 6-9
6.2.5 Exception Processing Sequence............................................................ 6-11
6.3 Processing of Specific Exceptions ............................................................. 6-11
6.3.1 Reset ...................................................................................................... 6-11
6.3.2 Interrupts ................................................................................................ 6-12
6.3.3 Uninitialized Interrupt.............................................................................. 6-13
6.3.4 Spurious Interrupt ................................................................................... 6-13
6.3.5 Instruction Traps..................................................................................... 6-13
6.3.6 Illegal and Unimplemented Instructions.................................................. 6-14
6.3.7 Privilege Violations ................................................................................. 6-15
6.3.8 Tracing.................................................................................................... 6-15
6.3.9 Bus Errors............................................................................................... 6-16
6.3.9.1 Bus Error............................................................................................. 6-16
6.3.9.2 Bus Error (MC68010) .......................................................................... 6-17
6.3.10 Address Error ......................................................................................... 6-19
6.4 Return From Exception (MC68010) ........................................................... 6-20
Section 7
8-Bit Instruction Timing
7.1 Operand Effective Address Calculation Times............................................ 7-1
7.2 Move Instruction Execution Times .............................................................. 7-2
7.3 Standard Instruction Execution Times......................................................... 7-3
7.4 Immediate Instruction Execution Times ...................................................... 7-4
7.5 Single Operand Instruction Execution Times.............................................. 7-5
7.6 Shift/Rotate Instruction Execution Times .................................................... 7-6
7.7 Bit Manipulation Instruction Execution Times ............................................. 7-7
7.8 Conditional Instruction Execution Times ..................................................... 7-7
7.9 JMP, JSR, LEA, PEA, and MOVEM Instruction Execution Times............... 7-8
7.10 Multiprecision Instruction Execution Times................................................. 7-8
7.11 Miscellaneous Instruction Execution Times ................................................ 7-9
7.12 Exception Processing Instruction Execution Times ................................... 7-10
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xM68000 USER’S MANUAL MOTOROLA
TABLE OF CONTENTS (Continued)
Paragraph Page
Number Title Number
Section 8
16-Bit Instruction Timing
8.1 Operand Effective Address Calculation Times ...........................................8-1
8.2 Move Instruction Execution Times..............................................................8-2
8.3 Standard Instruction Execution Times ........................................................8-3
8.4 Immediate Instruction Execution Times ......................................................8-4
8.5 Single Operand Instruction Execution Times..............................................8-5
8.6 Shift/Rotate Instruction Execution Times ....................................................8-6
8.7 Bit Manipulation Instruction Execution Times .............................................8-7
8.8 Conditional Instruction Execution Times.....................................................8-7
8.9 JMP, JSR, LEA, PEA, and MOVEM Instruction Execution Times .............. 8-8
8.10 Multiprecision Instruction Execution Times.................................................8-8
8.11 Miscellaneous Instruction Execution Times ................................................8-9
8.12 Exception Processing Instruction Execution Times ..................................8-10
Section 9
MC68010 Instruction Timing
9.1 Operand Effective Address Calculation Times ...........................................9-2
9.2 Move Instruction Execution Times..............................................................9-2
9.3 Standard Instruction Execution Times ........................................................9-4
9.4 Immediate Instruction Execution Times ......................................................9-6
9.5 Single Operand Instruction Execution Times..............................................9-6
9.6 Shift/Rotate Instruction Execution Times ....................................................9-8
9.7 Bit Manipulation Instruction Execution Times .............................................9-9
9.8 Conditional Instruction Execution Times.....................................................9-9
9.9 JMP, JSR, LEA, PEA, and MOVEM Instruction Execution Times ............9-10
9.10 Multiprecision Instruction Execution Times...............................................9-11
9.11 Miscellaneous Instruction Execution Times ..............................................9-11
9.12 Exception Processing Instruction Execution Times ..................................9-13
Section 10
Electrical and Thermal Characteristics
10.1 Maximum Ratings .....................................................................................10-1
10.2 Thermal Characteristics ............................................................................10-1
10.3 Power Considerations...............................................................................10-2
10.4 CMOS Considerations ..............................................................................10-4
10.5 AC Electrical Specifications Definitions.....................................................10-5
10.6 MC68000/68008/68010 DC Electrical Characteristics..............................10-7
10.7 DC Electrical Characteristics .................................................................... 10-8
10.8 AC Electrical Specifications—Clock Timing..............................................10-8
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MOTOROLA M68000 USER’S MANUAL xi
TABLE OF CONTENTS (Continued)
Paragraph Page
Number Title Number
Section 10
Electrical and Thermal Characteristics
10.9 MC68008 AC Electrical Specifications—Clock Timing .............................10-9
10.10 AC Electrical Specifications—Read and Write Cycles ............................10-10
10.11 AC Electrical Specifications—MC68000 To M6800 Peripheral...............10-15
10.12 AC Electrical Specifications—Bus Arbitration .........................................10-17
10.13 MC68EC000 DC Electrical Spec ifications..............................................10-23
10.14 MC68EC000 AC Electrical Specifications—Read and Write ..................10-24
10.15 MC68EC000 AC Electrical Specifications—Bus Arbitration....................10-28
Section 11
Ordering Information and Mechanical Data
11.1 Pin Assignments........................................................................................11-1
11.2 Package Dimensions ................................................................................11-7
Appendix A
MC68010 Loop Mode Operation
Appendix B
M6800 Peripheral Interface
B.1 Data Transfer Operation............................................................................. B-1
B.2 Interrupt Interface Operation ...................................................................... B-4
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xii M68000 USER’S MANUAL MOTOROLA
LIST OF ILLUSTRATIONS
Figure Page
Number Title Number
2-1 User Programmer's Model ................................................................................... 2-2
2-2 Supervisor Programmer's Model Supplement .....................................................2-2
2-3 Supervisor Programmer's Model Supplement (MC68010) ..................................2-3
2-4 Status Register ....................................................................................................2-3
2-5 Word Organization In Memory............................................................................. 2-6
2-6 Data Organization In Memory .............................................................................. 2-7
2-7 Memory Data Organization (MC68008) ............................................................... 2-3
3-1 Input and Output Signals (MC68000, MC68HC000, MC68010).......................... 3-1
3-2 Input and Output Signals ( MC68HC001) ............................................................3-2
3-3 Input and Output Signals (MC68EC000) .............................................................3-2
3-4 Input and Output Signals (MC68008 48-Pin Version).......................................... 3-3
3-5 Input and Output Signals (MC68008 52-Pin Version).......................................... 3-3
4-1 Byte Read-Cycle Flowchart..................................................................................4-2
4-2 Read and Write-Cycle Timing Diagram................................................................ 4-2
4-3 Byte Write-Cycle Flowchart..................................................................................4-4
4-4 Write-Cycle Timing Diagram ................................................................................ 4-4
4-5 Read-Modify-Write Cycle Flowchart .................................................................... 4-6
4-6 Read-Modify-Write Cycle Timing Diagram...........................................................4-7
5-1 Word Read-Cycle Flowchart ................................................................................ 5-2
5-2 Byte Read-Cycle Flowchart..................................................................................5-2
5-3 Read and Write-Cycle Timing Diagram................................................................ 5-3
5-4 Word and Byte Read-Cycle Timing Diagram .......................................................5-3
5-5 Word Write-Cycle Flowchart ................................................................................ 5-5
5-6 Byte Write-Cycle Flowchart..................................................................................5-5
5-7 Word and Byte Write-Cycle Timing Diagram .......................................................5-6
5-8 Read-Modify-Write Cycle Flowchart .................................................................... 5-7
5-9 Read-Modify-Write Cycle Timing Diagram...........................................................5-8
5-10 CPU Space Address Encoding ............................................................................5-9
5-11 Interrupt Acknowledge Cycle Timing Diagram...................................................5-10
5-12 Breakpoint Acknowledge Cycle Timing Diagram ...............................................5-11
5-13 3-Wire Bus Arbitration Flowchart
(NA to 48-Pin MC68008 and MC68EC000 ........................................................5-12
5-14 2-Wire Bus Arbitration Cycle Flowchart .............................................................5-13
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MOTOROLA M68000 USER’S MANUAL xiii
LIST OF ILLUSTRATIONS (Continued)
Figure Page
Number Title Number
5-15 3-Wire Bus Arbitration Timing Diagram
(NA to 48-Pin MC68008 and MC68EC000 ........................................................5-13
5-16 2-Wire Bus Arbitration Timing Diagram..............................................................5-14
5-17 External Asynchronous Signal Synchronization.................................................5-16
5-18 Bus Arbitration Unit State Diagrams...................................................................5-17
5-19 3-Wire Bus Arbitration Timing Diagram—Processor Active ...............................5-18
5-20 3-Wire Bus Arbitration Timing Diagram—Bus Active .........................................5-19
5-21 3-Wire Bus Arbitration Timing Diagram—Special Case .....................................5-20
5-22 2-Wire Bus Arbitration Timing Diagram—Processor Active ...............................5-21
5-23 2-Wire Bus Arbitration Timing Diagram—Bus Active .........................................5-22
5-24 2-Wire Bus Arbitration Timing Diagram—Special Case .....................................5-23
5-25 Bus Error Timing Diagram..................................................................................5-24
5-26 Delayed Bus Error Timing Diagram (MC68010).................................................5-25
5-27 Retry Bus Cycle Timing Diagram .......................................................................5-26
5-28 Delayed Retry Bus Cycle Timing Diagram.........................................................5-27
5-29 Halt Operation Timing Diagram..........................................................................5-28
5-30 Reset Operation Timing Diagram.......................................................................5-29
5-31 Fully Asynchronous Read Cycle ........................................................................5-32
5-32 Fully Asynchronous Write Cycle.........................................................................5-33
5-33 Pseudo-Asynchronous Read Cycle ...................................................................5-34
5-34 Pseudo-Asynchronous Write Cycle....................................................................5-35
5-35 Synchronous Read Cycle...................................................................................5-37
5-36 Synchronous Write Cycle...................................................................................5-38
5-37 Input Synchronizers ...........................................................................................5-38
6-1 Exception Vector Format...................................................................................... 6-4
6-2 Peripheral Vector Number Format .......................................................................6-5
6-3 Address Translated from 8-Bit Vector Number ...................................................6-5
6-4 Exception Vector Address Calculation (MC68010)..............................................6-5
6-5 Group 1 and 2 Exception Stack Frame..............................................................6-10
6-6 MC68010 Stack Frame ......................................................................................6-10
6-7 Supervisor Stack Order for Bus or Address Error Exception .............................6-17
6-8 Exception Stack Order (Bus and Address Error) ...............................................6-18
6-9 Special Status Word Format ..............................................................................6-19
10-1 MC68000 Power Dissipation (PD) vs Ambient Temperature (TA) .....................10-3
10-2 Drive Levels and Test Points for AC Specifications ...........................................10-6
10-3 Clock Input Timing Diagram ...............................................................................10-9
10-4 Read Cycle Timing Diagram ............................................................................10-13
10-5 Write Cycle Timing Diagram.............................................................................10-14
10-6 MC68000 to M6800 Peripheral Timing Diagram (Best Case)..........................10-16
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xiv M68000 USER’S MANUAL MOTOROLA
LIST OF ILLUSTRATIONS (Concluded)
Figure Page
Number Title Number
10-7 Bus Arbitration Timing...................................................................................... 10-18
10-8 Bus Arbitration Timing...................................................................................... 10-19
10-9 Bus Arbitration Timing—Idle Bus Case............................................................10-20
10-10 Bus Arbitration Timing—Active Bus Case........................................................10-21
10-11 Bus Arbitration Timing—Multiple Bus Request ................................................10-22
10-12 MC68EC000 Read Cycle Timing Diagram ......................................................10-26
10-13 MC68EC000 Write Cycle Timing Diagram.......................................................10-27
10-14 MC68EC000 Bus Arbitration Timing Diagram .................................................10-29
11-1 64-Pin Dual In Line ............................................................................................11-2
11-2 68-Lead Pin Grid Array ......................................................................................11-3
11-3 68-Lead Quad Pack ...........................................................................................11-4
11-4 52-Lead Quad Pack ...........................................................................................11-5
11-5 48-Pin Dual In Line ............................................................................................11-6
11-6 64-Lead Quad Flat Pack.................................................................................... 11-7
11-7 Case 740-03—L Suffix....................................................................................... 11-8
11-8 Case 767-02—P Suffix ...................................................................................... 11-9
11-9 Case 746-01—LC Suffix ..................................................................................11-10
11-10 Case — Suffix ......................................................................................................11-
11-11 Case 765A-05—RC Suffix ...............................................................................11-12
11-12 Case 778-02—FN Suffix..................................................................................11-13
11-13 Case 779-02—FN Suffix..................................................................................11-14
11-14 Case 847-01—FC Suffix..................................................................................11-15
11-15 Case 840B-01—FU Suffix................................................................................ 11-16
A-1 DBcc Loop Mode Program Example................................................................... A-1
B-1 M6800 Data Transfer Flowchart ......................................................................... B-1
B-2 Example External VMA Circuit............................................................................ B-2
B-3 External VMA Timing .......................................................................................... B-2
B-4 M6800 Peripheral Timing—Best Case................................................................ B-3
B-5 M6800 Peripheral Timing—Worst Case ............................................................. B-3
B-6 Autovector Operation Timing Diagram................................................................ B-5
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MOTOROLA M68000 USER’S MANUAL xv
LIST OF TABLES
Table Page
Number Title Number
2-1 Data Addressing Modes.......................................................................................2-4
2-2 Instruction Set Summary....................................................................................2-11
3-1 Data Strobe Control of Data Bus..........................................................................3-5
3-2 Data Strobe Control of Data Bus (MC68008).......................................................3-5
3-3 Function Code Output ..........................................................................................3-9
3-4 Signal Summary.................................................................................................3-10
5-1 DTACK, BERR, and HALT Assertion Results .....................................................5-31
6-1 Reference Classification.......................................................................................6-3
6-2 Exception Vector Assignment ..............................................................................6-7
6-3 Exception Grouping and Priority...........................................................................6-9
6-4 MC68010 Format Code......................................................................................6-11
7-1 Effective Address Calculation Times....................................................................7-2
7-2 Move Byte Instruction Execution Times ...............................................................7-2
7-3 Move Word Instruction Execution Times..............................................................7-3
7-4 Move Long Instruction Execution Times ..............................................................7-3
7-5 Standard Instruction Execution Times..................................................................7-4
7-6 Immediate Instruction Execution Times ...............................................................7-5
7-7 Single Operand Instruction Execution Times.......................................................7-6
7-8 Shift/Rotate Instruction Execution Times ............................................................. 7-6
7-9 Bit Manipulation Instruction Execution Times ......................................................7-7
7-10 Conditional Instruction Execution Times ..............................................................7-7
7-11 JMP, JSR, LEA, PEA, and MOVEM Instruction Execution Times........................7-8
7-12 Multiprecision Instruction Execution Times..........................................................7-9
7-13 Miscellaneous Instruction Execution Times .......................................................7-10
7-14 Move Peripheral Instruction Execution Times....................................................7-10
7-15 Exception Processing Instruction Execution Times ...........................................7-11
8-1 Effective Address Calculation Times....................................................................8-2
8-2 Move Byte Instruction Execution Times ...............................................................8-2
8-3 Move Word Instruction Execution Times..............................................................8-3
8-4 Move Long Instruction Execution Times ..............................................................8-3
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xvi M68000 USER’S MANUAL MOTOROLA
LIST OF TABLES (Concluded)
Table Page
Number Title Number
8-5 Standard Instruction Execution Times ................................................................. 8-4
8-6 Immediate Instruction Execution Times ............................................................... 8-5
8-7 Single Operand Instruction Execution Times.......................................................8-6
8-8 Shift/Rotate Instruction Execution Times ............................................................. 8-6
8-9 Bit Manipulation Instruction Execution Times ......................................................8-7
8-10 Conditional Instruction Execution Times..............................................................8-7
8-11 JMP, JSR, LEA, PEA, and MOVEM Instruction Execution Times ....................... 8-8
8-12 Multiprecision Instruction Execution Times..........................................................8-9
8-13 Miscellaneous Instruction Execution Times .......................................................8-10
8-14 Move Peripheral Instruction Execution Times....................................................8-10
8-15 Exception Processing Instruction Execution Times ...........................................8-11
9-1 Effective Address Calculation Times ...................................................................9-2
9-2 Move Byte and Word Instruction Execution Times ..............................................9-3
9-3 Move Byte and Word Instruction Loop Mode Execution Times ...........................9-3
9-4 Move Long Instruction Execution Times..............................................................9-4
9-5 Move Long Instruction Loop Mode Execution Times ...........................................9-4
9-6 Standard Instruction Execution Times ................................................................. 9-5
9-7 Standard Instruction Loop Mode Execution Times ..............................................9-5
9-8 Immediate Instruction Execution Times ............................................................... 9-6
9-9 Single Operand Instruction Execution Times.......................................................9-7
9-10 Clear Instruction Execution Times ....................................................................... 9-7
9-11 Single Operand Instruction Loop Mode Execution Times.................................... 9-8
9-12 Shift/Rotate Instruction Execution Times ............................................................. 9-8
9-13 Shift/Rotate Instruction Loop Mode Execution Times ..........................................9-9
9-14 Bit Manipulation Instruction Execution Times ......................................................9-9
9-15 Conditional Instruction Execution Times............................................................ 9-10
9-16 JMP, JSR, LEA, PEA, and MOVEM Instruction Execution Times .....................9-10
9-17 Multiprecision Instruction Execution Times........................................................9-11
9-18 Miscellaneous Instruction Execution Times .......................................................9-12
9-19 Exception Processing Instruction Execution Times ...........................................9-13
10-1 Power Dissipation and Junction Temperature vs Temperature
(θJC= θJA) ........................................................................................................10-4
10-2 Power Dissipation and Junction Temperature vs Temperature
(θJC= θJC)........................................................................................................10-4
A-1 MC68010 Loop Mode Instructions...................................................................... A-3
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MOTOROLA M68000 8-/16-/32-BIT MICROPROCESSORS USER’S MANUAL 1-1
SECTION 1
OVERVIEW
This manual includes hardware details and programming information for the MC68000,
the MC68HC000, the MC68HC001, the MC68008, the MC68010, and the MC68EC000.
For ease of reading, the name M68000 MPUs will be used when referring to all
processors. Refer to M68000PM/AD,
M68000 Programmer's Reference Manual , for
detailed information on the MC68000 instruction set.
The six microprocessors are very similar. They all contain the following features
• 16 32-Bit Data and Address Registers
• 16-Mbyte Direct Addressing Range
• Program Counter
• 6 Powerful Instruction Types
• Operations on Five Main Data Types
• Memory-Mapped Input/Output (I/O)
• 14 Addressing Modes
The following processors contain additional features:
• MC68010
—Virtual Memory/Machine Support
—High-Performance Looping Instructions
• MC68HC001/MC68EC000
—Statically Selectable 8- or 16-Bit Data Bus
• MC68HC000/MC68EC000/MC68HC001
—Low-Power
All the processors are basically the same with the exception of the MC68008. The
MC68008 differs from the others in that the data bus size is eight bits, and the address
range is smaller. The MC68010 has a few additional instructions and instructions that
operate differently than the corresponding instructions of the other devices.
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1-2 M68000 8-/16-/32-BIT MICROPROCESSORS USER’S MANUAL MOTOROLA
1.1 MC68000
The MC68000 is the first implementation of the M68000 16/-32 bit microprocessor
architecture. The MC68000 has a 16-bit data bus and 24-bit address bus while the full
architecture provides for 32-bit address and data buses. It is completely code-compatible
with the MC68008 8-bit data bus implementation of the M68000 and is upward code
compatible with the MC68010 virtual extensions and the MC68020 32-bit implementation
of the architecture. Any user-mode programs using the MC68000 instruction set will run
unchanged on the MC68008, MC68010, MC68020, MC68030, and MC68040. This is
possible because the user programming model is identical for all processors and the
instruction sets are proper subsets of the complete architecture.
1.2 MC68008
The MC68008 is a member of the M68000 family of advanced microprocessors. This
device allows the design of cost-effective systems using 8-bit data buses while providing
the benefits of a 32-bit microprocessor architecture. The performance of the MC68008 is
greater than any 8-bit microprocessor and superior to several 16-bit microprocessors.
The MC68008 is available as a 48-pin dual-in-line package (plastic or ceramic) and 52-pin
plastic leaded chip carrier. The additional four pins of the 52-pin package allow for
additional signals: A20, A21, BGACK, and IPL2. The 48-pin version supports a 20-bit
address that provides a 1-Mbyte address space; the 52-pin version supports a 22-bit
address that extends the address space to 4 Mbytes. The 48-pin MC68008 contains a
simple two-wire arbitration circuit; the 52-pin MC68008 contains a full three-wire MC68000
bus arbitration control. Both versions are designed to work with daisy-chained networks,
priority encoded networks, or a combination of these techniques.
A system implementation based on an 8-bit data bus reduces system cost in comparison
to 16-bit systems due to a more effective use of components and byte-wide memories and
peripherals. In addition, the nonmultiplexed address and data buses eliminate the need for
external demultiplexers, further simplifying the system.
The large nonsegmented linear address space of the MC68008 allows large modular
programs to be developed and executed efficiently. A large linear address space allows
program segment sizes to be determined by the application rather than forcing the
designer to adopt an arbitrary segment size without regard to the application's individual
requirements.
1.3 MC68010
The MC68010 utilizes VLSI technology and is a fully implemented 16-bit microprocessor
with 32-bit registers, a rich basic instruction set, and versatile addressing modes. The
vector base register (VBR) allows the vector table to be dynamically relocated
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MOTOROLA M68000 8-/16-/32-BIT MICROPROCESSORS USER’S MANUAL 1-3
1.4 MC68HC000
The primary benefit of the MC68HC000 is reduced power consumption. The device
dissipates an order of magnitude less power than the HMOS MC68000.
The MC68HC000 is an implementation of the M68000 16/-32 bit microprocessor
architecture. The MC68HC000 has a 16-bit data bus implementation of the MC68000 and
is upward code-compatible with the MC68010 virtual extensions and the MC68020 32-bit
implementation of the architecture.
1.5 MC68HC001
The MC68HC001 provides a functional extension to the MC68HC000 HCMOS 16-/32-bit
microprocessor with the addition of statically selectable 8- or 16-bit data bus operation.
The MC68HC001 is object-code compatible with the MC68HC000, and code written for
the MC68HC001 can be migrated without modification to any member of the M68000
Family.
1.6 MC68EC000
The MC68EC000 is an economical high-performance embedded controller designed to
suit the needs of the cost-sensitive embedded controller market. The HCMOS
MC68EC000 has an internal 32-bit architecture that is supported by a statically selectable
8- or 16-bit data bus. This architecture provides a fast and efficient processing device that
can satisfy the requirements of sophisticated applications based on high-level languages.
The MC68EC000 is object-code compatible with the MC68000, and code written for the
MC68EC000 can be migrated without modification to any member of the M68000 Family.
The MC68EC000 brings the performance level of the M68000 Family to cost levels
previously associated with 8-bit microprocessors. The MC68EC000 benefits from the rich
M68000 instruction set and its related high code density with low memory bandwidth
requirements.
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MOTOROLA M68000 8-/16-/32-BIT MICROPROCESSOR USER’S MANUAL 2-1
SECTION 2
INTRODUCTION
The section provide a brief introduction to the M68000 microprocessors (MPUs).
Detailed information on the programming model, data types, addressing modes, data
organization and instruction set can be found in M68000PM/AD,
M68000 Programmer's
Reference Manual
. All the processors are identical from the programmer's viewpoint,
except that the MC68000 can directly access 16 Mbytes (24-bit address) and the
MC68008 can directly access 1 Mbyte (20-bit address on 48-pin version or 22-bit
address on 52-pin version). The MC68010, which also uses a 24-bit address, has much
in common with the other devices; however, it supports additional instructions and
registers and provides full virtual machine/memory capability. Unless noted, all
information pertains to all the M68000 MPUs.
2.1 PROGRAMMER'S MODEL
All the microprocessors executes instructions in one of two modes—user mode or
supervisor mode. The user mode provides the execution environment for the majority of
application programs. The supervisor mode, which allows some additional instructions
and privileges, is used by the operating system and other system software.
2.1.1 User' Programmer's Model
The user programmer's model (see Figure 2-1) is common to all M68000 MPUs. The
user programmer's model, contains 16, 32-bit, general-purpose registers (D0–D7, A0–
A7), a 32-bit program counter, and an 8-bit condition code register. The first eight
registers (D0–D7) are used as data registers for byte (8-bit), word (16-bit), and long-word
(32-bit) operations. The second set of seven registers (A0–A6) and the user stack pointer
(USP) can be used as software stack pointers and base address registers. In addition,
the address registers can be used for word and long-word operations. All of the 16
registers can be used as index registers.
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2-2 M68000 8-/16-/32-BIT MICROPROCESSOR USER’S MANUAL MOTOROLA
31 16 15 8 7 0
31 16 15 0
D0
D1
D2
D3
D4
D5
D6
D7
A1
A2
A3
A4
A5
A6
A0
A7
(USP) POINTER
PC
CCR STATUS
REGISTER
PROGRAM
COUNTER
USER STACK
SEVEN
ADDRESS
REGISTERS
EIGHT
DATA
REGISTERS
31
70
0
Figure 2-1. User Programmer's Model
(MC68000/MC68HC000/MC68008/MC68010)
2.1.2 Supervisor Programmer's Model
The supervisor programmer's model consists of supplementary registers used in the
supervisor mode. The M68000 MPUs contain identical supervisor mode register
resources, which are shown in Figure 2-2, including the status register (high-order byte)
and the supervisor stack pointer (SSP/A7').
SUPERVISOR STACK
POINTER
31 16 15 0
15 8 7 0 STATUS REGISTER
A7'
(SSP)
SR
CCR
Figure 2-2. Supervisor Programmer's Model Supplement
The supervisor programmer's model supplement of the MC68010 is shown in Figure 2-
3. In addition to the supervisor stack pointer and status register, it includes the vector
base register (VRB) and the alternate function code registers (AFC).The VBR is used to
determine the location of the exception vector table in memory to support multiple vector
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MOTOROLA M68000 8-/16-/32-BIT MICROPROCESSOR USER’S MANUAL 2-3
tables. The SFC and DFC registers allow the supervisor to access user data space or
emulate CPU space cycles.
31 16 15 0
15 8 7 0
A7'
(SSP) SUPERVISOR STACK POINTER
CCR SR STATUS REGISTER
31 0
VBR VECTOR BASE REGISTER
20
SFC
DFC ALTERNATE FUNCTION
CODE REGISTERS
Figure 2-3. Supervisor Programmer's Model Supplement
(MC68010)
2.1.3 Status Register
The status register (SR),contains the interrupt mask (eight levels available) and the
following condition codes: overflow (V), zero (Z), negative (N), carry (C), and extend (X).
Additional status bits indicate that the processor is in the trace (T) mode and/or in the
supervisor (S) state (see Figure 2-4). Bits 5, 6, 7, 11, 12, and 14 are undefined and
reserved for future expansion
TSIII XNZVC 210
15 13 10 8 4 0
TRACE MODE
SUPERVISOR
STATE
INTERRUPT
MASK
EXTEND
NEGATIVE
ZERO
OVERFLOW
CARRY
CONDITION
CODES
SYSTEM BYTE USER BYTE
Figure 2-4. Status Register
2.2 DATA TYPES AND ADDRESSING MODES
The five basic data types supported are as follows:
1. Bits
2. Binary-Coded-Decimal (BCD) Digits (4 Bits)
3. Bytes (8 Bits)
4. Words (16 Bits)
5. Long Words (32 Bits)
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2-4 M68000 8-/16-/32-BIT MICROPROCESSOR USER’S MANUAL MOTOROLA
In addition, operations on other data types, such as memory addresses, status word
data, etc., are provided in the instruction set.
The 14 flexible addressing modes, shown in Table 2-1, include six basic types:
1. Register Direct
2. Register Indirect
3. Absolute
4. Immediate
5. Program Counter Relative
6. Implied
The register indirect addressing modes provide postincrementing, predecrementing,
offsetting, and indexing capabilities. The program counter relative mode also supports
indexing and offsetting. For detail information on addressing modes refer to
M68000PM/AD,
M68000 Programmer Reference Manual .
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MOTOROLA M68000 8-/16-/32-BIT MICROPROCESSOR USER’S MANUAL 2-5
Table 2-1. Data Addressing Modes
Mode Generation Syntax
Register Direct Addressing
Data Register Direct
Address Register Direct EA=Dn EA=An Dn An
Absolute Data Addressing
Absolute Short
Absolute Long EA = (Next Word) EA = (Next Two Words) (xxx).W (xxx).L
Program Counter Relative
Addressing
Relative with Offset
Relative with Index and Offset
EA = (PC)+d16
EA = (PC)+d8(d16,PC) (d8,PC,Xn)
Register Indirect Addressing
Register Indirect
Postincrement Register Indirect
Predecrement Register Indirect
Register Indirect with Offset
Indexed Register Indirect with Offset
EA = (An)
EA = (An), An ←An+N
An ¯An–N, EA=(An)
EA = (An)+d16
EA = (An)+(Xn)+d8
(An)
(An)+
-(An)
(d16,An)
(d8,An,Xn)
Immediate Data Addressing
Immediate
Quick Immediate DATA = Next Word(s) Inherent Data #<data>
Implied Addressing1
Implied Register EA = SR, USP, SSP, PC,
VBR, SFC, DFC SR,USP,SSP,PC, VBR, SFC,DFC
NOTES: 1. The VBR, SFC, and DFC apply to the MC68010 only
EA = Effective Address
Dn = Data Register
An = Address Register
( ) = Contents of
PC = Program Counter
d8= 8-Bit Offset (Displacement)
d16 = 16-Bit Offset (Displacement)
N = 1 for byte, 2 for word, and 4 for long word. If An is the stack pointer and
the operand size is byte, N = 2 to keep the stack pointer on a word boundary.
¯= Replaces
Xn = Address or Data Register used as Index Register
SR = Status Register
USP = User Stack Pointer
SSP = Supervisor Stack Pointer
CP = Program Counter
VBR = Vector Base Register
2.3 DATA ORGANIZATION IN REGISTERS
The eight data registers support data operands of 1, 8, 16, or 32 bits. The seven address
registers and the active stack pointer support address operands of 32 bits.
2.3.1 Data Registers
Each data register is 32 bits wide. Byte operands occupy the low-order 8 bits, word
operands the low-order 16 bits, and long-word operands, the entire 32 bits. The least
significant bit is addressed as bit zero; the most significant bit is addressed as bit 31.
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2-6 M68000 8-/16-/32-BIT MICROPROCESSOR USER’S MANUAL MOTOROLA
When a data register is used as either a source or a destination operand, only the
appropriate low-order portion is changed; the remaining high-order portion is neither
used nor changed.
2.3.2 Address Registers
Each address register (and the stack pointer) is 32 bits wide and holds a full, 32-bit
address. Address registers do not support byte-sized operands. Therefore, when an
address register is used as a source operand, either the low-order word or the entire
long-word operand is used, depending upon the operation size. When an address
register is used as the destination operand, the entire register is affected, regardless of
the operation size. If the operation size is word, operands are sign-extended to 32 bits
before the operation is performed.
2.4 DATA ORGANIZATION IN MEMORY
Bytes are individually addressable. As shown in Figure 2-5, the high-order byte of a
word has the same address as the word. The low-order byte has an odd address, one
count higher. Instructions and multibyte data are accessed only on word (even byte)
boundaries. If a long-word operand is located at address n (n even), then the second
word of that operand is located at address n+2.
BYTE 000000 BYTE 000001
WORD 0
WORD 1 BYTE 000003
BYTE 000002
BYTE FFFFFE
BYTE FFFFFE WORD 7FFFFF
1514131211109876543210
ADDRESS
$000000
$000002
$FFFFFE
Figure 2-5. Word Organization in Memory
The data types supported by the M68000 MPUs are bit data, integer data of 8, 16, and
32 bits, 32-bit addresses, and binary-coded-decimal data. Each data type is stored in
memory as shown in Figure 2-6. The numbers indicate the order of accessing the data
from the processor. For the MC68008 with its 8-bit bus, the appearance of data in
memory is identical to the all the M68000 MPUs. The organization of data in the memory
of the MC68008 is shown in Figure 2-7.
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