AT91SAM9G45-EKES Atmel, AT91SAM9G45-EKES Datasheet - Page 36

• Manufacturer Part Number: AT91SAM9G45-EKES
• Description: KIT EVAL FOR AT91SAM9G45
• Manufacturer: Atmel
• Series: AT91SAM Smart ARMr
• Type: MCUr

Specifications of AT91SAM9G45-EKES

• Contents: Board
• Processor To Be Evaluated: SAM9G45
• Data Bus Width: 32 bit
• Interface Type: I2C, SPI, UART
• Maximum Operating Temperature: + 50 C
• Minimum Operating Temperature: - 10 C
• Operating Supply Voltage: 1.8 V to 3.3 V
• For Use With/related Products: AT91SAM9G45
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: Q4626953

36
AT91SAM9G45
Table 9-1.
The ARM state register set contains 16 directly-accessible registers, r0 to r15, and an additional
register, the Current Program Status Register (CPSR). Registers r0 to r13 are general-purpose
registers used to hold either data or address values. Register r14 is used as a Link register that
holds a value (return address) of r15 when BL or BLX is executed. Register r15 is used as a pro-
gram counter (PC), whereas the Current Program Status Register (CPSR) contains condition
code flags and the current mode bits.
In privileged modes (FIQ, Supervisor, Abort, IRQ, Undefined), mode-specific banked registers
(r8 to r14 in FIQ mode or r13 to r14 in the other modes) become available. The corresponding
banked registers r14_fiq, r14_svc, r14_abt, r14_irq, r14_und are similarly used to hold the val-
ues (return address for each mode) of r15 (PC) when interrupts and exceptions arise, or when
BL or BLX instructions are executed within interrupt or exception routines. There is another reg-
ister called Saved Program Status Register (SPSR) that becomes available in privileged modes
instead of CPSR. This register contains condition code flags and the current mode bits saved as
a result of the exception that caused entry to the current (privileged) mode.
In all modes and due to a software agreement, register r13 is used as stack pointer.
The use and the function of all the registers described above should obey ARM Procedure Call
Standard (APCS) which defines:
For more details, refer to ARM Software Development Kit.
The Thumb state register set is a subset of the ARM state set. The programmer has direct
access to:
System Mode
• constraints on the use of registers
• stack conventions
• argument passing and result return
• Eight general-purpose registers r0-r7
• Stack pointer, SP
• Link register, LR (ARM r14)
• PC
User and
CPSR
R12
R13
R14
PC
ARM9TDMI Modes and Registers Layout
Supervisor
SPSR_SVC
R13_SVC
R14_SVC
CPSR
Mode
R12
PC
SPSR_ABOR
R13_ABORT
R14_ABORT
Abort Mode
CPSR
R12
PC
T
SPSR_UNDE
R13_UNDEF
R14_UNDEF
Undefined
CPSR
Mode
R12
PC
F
Mode-specific banked registers
SPSR_IRQ
Interrupt
R13_IRQ
R14_IRQ
CPSR
Mode
R12
PC
6438F–ATARM–21-Jun-10
Fast Interrupt
SPSR_FIQ
R12_FIQ
R13_FIQ
R14_FIQ
CPSR
Mode
PC