- •Introduction
- •ARM7TDMI Architecture
- •The THUMB Concept
- •THUMB’s Advantages
- •ARM7TDMI Block Diagram
- •ARM7TDMI Core Diagram
- •ARM7TDMI Functional Diagram
- •Key to signal types
- •Processor Operating States
- •Switching State
- •Entering THUMB state
- •Entering ARM state
- •Memory Formats
- •Big endian format
- •Little endian format
- •Instruction Length
- •Data Types
- •Operating Modes
- •Registers
- •The ARM state register set
- •The THUMB state register set
- •The relationship between ARM and THUMB state registers
- •Accessing Hi registers in THUMB state
- •The Program Status Registers
- •The condition code flags
- •The control bits
- •Exceptions
- •Action on entering an exception
- •Action on leaving an exception
- •Exception entry/exit summary
- •Notes
- •Abort
- •Software interrupt
- •Undefined instruction
- •Exception vectors
- •Exception priorities
- •Not all exceptions can occur at once:
- •Interrupt Latencies
- •Reset
- •Instruction Set Summary
- •Format summary
- •Instruction summary
- •The Condition Field
- •Branch and Exchange (BX)
- •Instruction cycle times
- •Assembler syntax
- •Using R15 as an operand
- •Examples
- •Branch and Branch with Link (B, BL)
- •The link bit
- •Instruction cycle times
- •Assembler syntax
- •Examples
- •Data Processing
- •CPSR flags
- •Shifts
- •Instruction specified shift amount
- •Register specified shift amount
- •Immediate operand rotates
- •Writing to R15
- •Using R15 as an operand
- •TEQ, TST, CMP and CMN opcodes
- •Instruction cycle times
- •Assembler syntax
- •where:
- •Examples
- •PSR Transfer (MRS, MSR)
- •Operand restrictions
- •Reserved bits
- •Example
- •Instruction cycle times
- •Assembler syntax
- •Examples
- •Multiply and Multiply-Accumulate (MUL, MLA)
- •If the operands are interpreted as signed
- •If the operands are interpreted as unsigned
- •Operand restrictions
- •CPSR flags
- •Instruction cycle times
- •Assembler syntax
- •Examples
- •Multiply Long and Multiply-Accumulate Long (MULL,MLAL)
- •Operand restrictions
- •CPSR flags
- •Instruction cycle times
- •For signed instructions SMULL, SMLAL:
- •For unsigned instructions UMULL, UMLAL:
- •Assembler syntax
- •where:
- •Examples
- •Single Data Transfer (LDR, STR)
- •Offsets and auto-indexing
- •Shifted register offset
- •Bytes and words
- •Little endian configuration
- •Big endian configuration
- •Restriction on the use of base register
- •Example:
- •Data aborts
- •Instruction cycle times
- •Assembler syntax
- •Examples
- •Halfword and Signed Data Transfer(LDRH/STRH/LDRSB/LDRSH)
- •Offsets and auto-indexing
- •Halfword load and stores
- •Signed byte and halfword loads
- •Endianness and byte/halfword selection
- •Little endian configuration
- •Big endian configuration
- •Data aborts
- •Instruction cycle times
- •Assembler syntax
- •Examples
- •Block Data Transfer (LDM, STM)
- •The register list
- •Addressing modes
- •Address alignment
- •LDM with R15 in transfer list and S bit set (Mode changes)
- •STM with R15 in transfer list and S bit set (User bank transfer)
- •R15 not in list and S bit set (User bank transfer)
- •Use of R15 as the base
- •Inclusion of the base in the register list
- •Data aborts
- •Aborts during STM instructions
- •Aborts during LDM instructions
- •Instruction cycle times
- •Assembler syntax
- •Addressing mode names
- •Examples
- •Single Data Swap (SWP)
- •Bytes and words
- •Data aborts
- •Instruction cycle times
- •Assembler syntax
- •Examples
- •Software Interrupt (SWI)
- •Return from the supervisor
- •Comment field
- •Instruction cycle times
- •Assembler syntax
- •Examples
- •Supervisor code
- •Coprocessor Data Operations (CDP)
- •The coprocessor fields
- •Instruction cycle times
- •Assembler syntax
- •Examples
- •Coprocessor Data Transfers (LDC, STC)
- •The coprocessor fields
- •Addressing modes
- •Address alignment
- •Data aborts
- •Instruction cycle times
- •Assembler syntax
- •Examples
- •Coprocessor Register Transfers (MRC, MCR)
- •The coprocessor fields
- •Transfers to R15
- •Transfers from R15
- •Instruction cycle times
- •Assembler syntax
- •Examples
- •Undefined Instruction
- •Instruction cycle times
- •Assembler syntax
- •Instruction Set Examples
- •Using the conditional instructions
- •Using conditionals for logical OR
- •Absolute value
- •Multiplication by 4, 5 or 6 (run time)
- •Combining discrete and range tests
- •Division and remainder
- •Overflow detection in the ARM7TDMI
- •Pseudo-random binary sequence generator
- •Multiplication by constant using the barrel shifter
- •Multiplication by 2^n (1,2,4,8,16,32..)
- •Multiplication by 2^n+1 (3,5,9,17..)
- •Multiplication by 2^n-1 (3,7,15..)
- •Multiplication by 6
- •Multiply by 10 and add in extra number
- •General recursive method for Rb := Ra*C, C a constant:
- •Loading a word from an unknown alignment
- •Format Summary
- •Opcode Summary
- •Format 1: move shifted register
- •Operation
- •Instruction cycle times
- •Examples
- •Format 2: add/subtract
- •Operation
- •Instruction cycle times
- •Examples
- •Format 3: move/compare/add/subtract immediate
- •Operations
- •Instruction cycle times
- •Examples
- •Format 4: ALU operations
- •Operation
- •Instruction cycle times
- •Examples
- •Format 5: Hi register operations/branch exchange
- •Operation
- •Instruction cycle times
- •The BX instruction
- •Examples
- •Using R15 as an operand
- •Format 6: PC-relative load
- •Operation
- •Instruction cycle times
- •Examples
- •Format 7: load/store with register offset
- •Operation
- •Instruction cycle times
- •Examples
- •Format 8: load/store sign-extended byte/halfword
- •Operation
- •Instruction cycle times
- •Examples
- •Format 9: load/store with immediate offset
- •Operation
- •Instruction cycle times
- •Examples
- •Format 10: load/store halfword
- •Operation
- •Instruction cycle times
- •Examples
- •Format 11: SP-relative load/store
- •Operation
- •Instruction cycle times
- •Examples
- •Format 12: load address
- •Operation
- •Instruction cycle times
- •Examples
- •Format 13: add offset to Stack Pointer
- •Operation
- •Instruction cycle times
- •Examples
- •Format 14: push/pop registers
- •Operation
- •Instruction cycle times
- •Examples
- •Format 15: multiple load/store
- •Operation
- •Instruction cycle times
- •Examples
- •Format 16: conditional branch
- •Operation
- •Instruction cycle times
- •Examples
- •Format 17: software interrupt
- •Operation
- •Instruction cycle times
- •Examples
- •Format 18: unconditional branch
- •Operation
- •Examples
- •Format 19: long branch with link
- •Operation
- •Instruction cycle times
- •Examples
- •Instruction Set Examples
- •Multiplication by a constant using shifts and adds
- •General purpose signed divide
- •Thumb code
- •ARM code
- •Division by a constant
- •Explanation of divide-by-constant ARM code
- •ARM code
- •THUMB code
- •Overview
- •Cycle Types
- •Address Timing
- •Data Transfer Size
- •Instruction Fetch
- •Memory Management
- •Locked Operations
- •Stretching Access Times
- •The ARM Data Bus
- •The External Data Bus
- •The unidirectional data bus
- •The bidirectional data bus
- •Example system: The ARM7TDMI Testchip
- •Overview
- •Interface Signals
- •Coprocessor present/absent
- •Busy-waiting
- •Pipeline following
- •Data transfer cycles
- •Register Transfer Cycle
- •Privileged Instructions
- •Idempotency
- •Undefined Instructions
- •Debug Interface
- •Overview
- •Debug Systems
- •Debug Interface Signals
- •Entry into debug state
- •Entry into debug state on breakpoint
- •Entry into debug state on watchpoint
- •Entry into debug state on debug-request
- •Action of ARM7TDMI in debug state
- •Scan Chains and JTAG Interface
- •Scan limitations
- •Scan chain 0
- •Scan chain 1
- •Scan Chain 2
- •The JTAG state machine
- •Reset
- •Pullup Resistors
- •Instruction Register
- •Public Instructions
- •EXTEST (0000)
- •SCAN_N (0010)
- •INTEST (1100)
- •IDCODE (1110)
- •BYPASS (1111)
- •CLAMP (0101)
- •HIGHZ (0111)
- •CLAMPZ (1001)
- •SAMPLE/PRELOAD (0011)
- •RESTART (0100)
- •Test Data Registers
- •Bypass register
- •ARM7TDMI device identification (ID) code register
- •Operating mode:
- •Instruction register
- •Scan chain select register
- •Scan chains 0,1 and 2
- •Scan chain 0 and 1
- •Scan chain 0
- •Scan chain 1
- •Scan chain 3
- •ARM7TDMI Core Clocks
- •Clock switch during debug
- •Clock switch during test
- •Determining the Core and System State
- •Determining the core’s state
- •Determining system state
- •Exit from debug state
- •The PC’s Behaviour During Debug
- •Breakpoint
- •Watchpoints
- •Watchpoint with another exception
- •Debug request
- •System speed access
- •Summary of return address calculations
- •Priorities / Exceptions
- •Breakpoint with prefetch abort
- •Interrupts
- •Data aborts
- •Scan Interface Timing
- •Debug Timing
- •Overview
- •The Watchpoint Registers
- •Programming and reading watchpoint registers
- •Using the mask registers
- •The control registers
- •Programming Breakpoints
- •Hardware breakpoints:
- •Software breakpoints:
- •Hardware breakpoints
- •Software breakpoints
- •Setting the breakpoint
- •Clearing the breakpoint
- •Programming Watchpoints
- •The Debug Control Register
- •Debug Status Register
- •Coupling Breakpoints and Watchpoints
- •Example
- •CHAINOUT signal
- •RANGEOUT signal
- •Example
- •Disabling ICEBreaker
- •ICEBreaker Timing
- •Programming Restriction
- •Debug Communications Channel
- •Debug comms channel registers
- •Communications via the comms channel
- •Introduction
- •Branch and Branch with Link
- •THUMB Branch with Link
- •Branch and Exchange (BX)
- •Data Operations
- •Multiply and Multiply Accumulate
- •Load Register
- •Store Register
- •Load Multiple Registers
- •Store Multiple Registers
- •Data Swap
- •Software Interrupt and Exception Entry
- •Coprocessor Data Operation
- •Coprocessor Data Transfer (from memory to coprocessor)
- •Coprocessor Data Transfer (from coprocessor to memory)
- •Coprocessor Register Transfer (Load from coprocessor)
- •Coprocessor Register Transfer (Store to coprocessor)
- •Undefined Instructions and Coprocessor Absent
- •Unexecuted Instructions
- •Instruction Speed Summary
- •Timing Diagrams
Instruction Set
Examples
SWI |
ReadC |
; Get next |
character |
from read stream. |
||
SWI |
WriteI+”k” |
; Output |
a |
“k” to the write stream. |
||
SWINE |
0 |
; |
Conditionally call |
supervisor |
||
|
|
; |
with 0 |
in comment field. |
||
Supervisor code
The previous examples assume that suitable supervisor code exists, for instance:
0x08 B |
Supervisor |
; SWI entry point |
|
EntryTable |
|
; addresses of supervisor routines |
|
|
DCD |
ZeroRtn |
|
|
DCD |
ReadCRtn |
|
|
DCD |
WriteIRtn |
|
|
. . . |
|
|
Zero |
EQU |
0 |
|
ReadC |
EQU |
256 |
|
WriteI |
EQU |
512 |
|
Supervisor
;SWI has routine required in bits 8-23 and data (if any) in
;bits 0-7.
;Assumes R13_svc points to a suitable stack
STMFD |
R13,{R0-R2,R14} |
; Save work |
registers and return |
|
|
; address. |
|
LDR |
R0,[R14,#-4] |
; Get SWI instruction. |
|
BIC |
R0,R0,#0xFF000000 ; Clear top |
8 bits. |
|
MOV |
R1,R0,LSR#8 |
; Get routine offset. |
|
ADR |
R2,EntryTable |
; Get start |
address of entry table. |
LDR |
R15,[R2,R1,LSL#2] ; Branch to |
appropriate routine. |
|
|
WriteIRtn |
; Enter with character in R0 bits 0-7. |
|
|
. . . . . . |
|
|
LDMFD |
R13,{R0-R2,R15}^ |
; Restore workspace and return, |
|
|
|
; restoring processor mode and flags. |
|
65
