2. ARM Ltd
ARM
Advanced RISC Machines
Founded in November 1990
Spun out of Acorn Computers
Company headquarters in Cambridge, UK
Processor design centres in Cambridge, Austin, and Sophia Antipolis
Sales, support, and engineering offices all over the world
Best known for its range of RISC processor cores designs
Other products – fabric IP, software tools, models, cell libraries - to
help partners develop and ship ARM-based SoCs
ARM does not manufacture silicon
4.
In 2005 about 98 percent of all mobile phones use at
least one ARM-designed core on their motherboards,
according to research from the analyst firm the Linley
Group
13. •
•
• Later Intel bought Strong
ARM From DEC & Changed
the name to Xscale .
• In 2006 Marvell Technology
Group bought Xscale from
Intel .
14.
15.
16.
17. Embedded ARM Cortex
Processors
• Cortex M0:
Ultra low gate
count (less that 12
K). gates).
Ultra low-power (3
μW/MHz ).
32-bit processor.
Based on ARMv6-
M architecture.
18. Embedded ARM Cortex
Processors
• Cortex M1:
The first ARM
processor designed
specifically for
implementation in
FPGAs.
Supports all major
FPGA vendors.
Easy migration path
from FPGA to ASIC.
Based on ARMv6-M
architecture.
19. Embedded ARM Cortex
Processors• Cortex M3:
The mainstream ARM
processor for
microcontroller
applications.
High performance
and energy efficiency.
Easy migration path
from FPGA to ASIC.
Advanced3-Stage
Pipeline.
Based on ARMv7-M
architecture.
20. Embedded ARM Cortex
Processors• Cortex M4:
Embedded processor for DSP.
FPU (Floating Point Unit).
Based on ARMv7E-M architecture.
24. Registers
ARM has a load store (RISC) architecture.
General purpose registers can hold data or
address.
In Arm cortex-M4 there are 21 Registers Visible
each 32bit wide:
Sixteen registers located in the register bank.
Five special registers located outside of the
register bank.
26. Registers
All 13 general-purpose registers can be used to
store instruction ,data & addresses .
These registers divided into :
Low Register from R0 to R7.
High Register from R8 to R12.
Most 16-bit data operations should be
performed in the Low Register group.
Most 32-bit data operations should be
processed in the High Register group.
27. Registers
R13 is a Stack Pointer
Register (SPR) used to
store the current stack
address.
In Cortex-M4 core, there are two kinds of stack pointers:
the Main Stack Pointer (MSP) : is used for the system program
working in the Handler Mode .
Process Stack Pointer (PSP) : is used for the user’s program
working in the Thread Mode.
Only one stack pointer is active at a time. The default
Stack Pointer is the MSP after the system is reset.
28. Registers
R14 is a Link Register (LR) : provides some
linking functions to set up a connection
between the main program and the calling
functions or subroutines.
When a function or subroutine is called, the
returning address should be entered into the R14.
After the function or subroutine is done, the content
of the Link Register R14, which is the returning
address to the main program, is fed into the
Program Counter (PC) to enable the processor to
continue the work from the address stored in the PC.
R15 is the Program Counter :points to the
address of the next instruction to be executed .
29. Registers
(XPSR) The Program Status Register : can be
divided into three different status registers to
show the running status of different units:
Application Program Status Register (APSR)
Execution Program Status Register (EPSR)
Interrupt Program Status Register (IPSR)
33. Processor Modes
ARM has seven basic operating modes
Each mode has access to its own stack space and a different subset of registers
Some operations can only be carried out in a privileged mode
Mode Description
Supervisor
(SVC)
Entered on reset and when a Supervisor call
instruction (SVC) is executed
Privileged
modes
FIQ
Entered when a high priority (fast) interrupt is
raised
IRQ Entered when a normal priority interrupt is raised
Abort Used to handle memory access violations
Undef Used to handle undefined instructions
System
Privileged mode using the same registers as User
mode
User
Mode under which most Applications / OS tasks
run
Unprivileged
mode
Exceptionmodes
34. AMBA
The Advanced Microcontroller Bus
Architecture
Three distinct buses are defined within
the AMBA specification:
the Advanced High-performance Bus
(AHB)
the Advanced System Bus (ASB)
the Advanced Peripheral Bus (APB).
35. AMBA
High Performance
ARM processor
High-bandwidth
on-chip RAM
High
Bandwidth
External
Memory
Interface
DMA
Bus Master
APB
Bridge
Timer
Keypad
UART
PIO
AHB or
ASB
APB
AHB
High performance
Pipelined operation
Burst Transfers
Multiple Bus Masters
APB
Low power
Latched address/control
Simple interface
Suitable of many
peripherals
ASB
High performance
Pipelined operation
38. Memory
8 Bit Width=1
Byte
• Arm cortex-M4 has 32-bit Address
bus ,that allow to Access 4 Gb
location in memory.
• The bus interface between the MCU
and external memory is the (AHB),
which provides interfaces and
connections to various 32/16/8-bit
memory devices.
• The following buses can be used to
access memory or peripheral devices
in parallel :
I-Code Bus: Fetch Opcode from the
flash ROM.
D-Code Bus: Read constant data from
flash ROM.
System Bus: Read/Write data from
SRAM or I/O, fetch opcode from
39. Memory
• The Cortex-M4 processors can work with either little endian or
big endian memory systems. Generally, the Cortex-M4 is
designed with just one endian configuration.
40. Stack Memory
• Stack is a kind of memory usage mechanism that allows a
portion of memory to be used as Last-In-First-Out data storage
buffer.
• PUSH to store data in stack .
• POP to retrieve data from stack
