NXP Semiconductors LPC1102, User Manual

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User manual Rev. 1 — 20 October 2010 179 of 258
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Chapter 19: Appendix LPC1102 ARM Cortex-M0 reference
On reset, the processor loads the MSP with the value from address
0x00000000
.
19.3.1.3.3 Link Register
The Link Register (LR) is register R14. It stores the return information for subroutines,
function calls, and exceptions. On reset, the LR value is Unknown.
19.3.1.3.4 Program Counter
The Program Counter (PC) is register R15. It contains the current program address. On
reset, the processor loads the PC with the value of the reset vector, which is at address
0x00000004
. Bit[0] of the value is loaded into the EPSR T-bit at reset and must be 1.
19.3.1.3.5 Program Status Register
The Program Status Register (PSR) combines:
•
Application Program Status Register (APSR)
•
Interrupt Program Status Register (IPSR)
•
Execution Program Status Register (EPSR).
These registers are mutually exclusive bitfields in the 32-bit PSR. The PSR bit
assignments are:
Access these registers individually or as a combination of any two or all three registers,
using the register name as an argument to the
MSR
or
MRS
instructions. For example:
•
read all of the registers using
PSR
with the
MRS
instruction
•
write to the APSR using
APSR
with the
MSR
instruction.
The PSR combinations and attributes are:
[1] The processor ignores writes to the IPSR bits.
[2] Reads of the EPSR bits return zero, and the processor ignores writes to the these bits
Fig 37. APSR, IPSR, EPSR register bit assignments
Table 193. PSR register combinations
Register Type Combination
PSR RW
[1][2]
APSR, EPSR, and IPSR
IEPSR RO EPSR and IPSR
IAPSR RW
[1]
APSR and IPSR
EAPSR RW
[2]
APSR and EPSR
25 24 23
Reserved Exception number
31 30 29 28 27
N Z C V
0
Reserved APSR
IPSR
EPSR Reserved Reserved T
5 6