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S3C2501X
PROGRAMMER'S MODEL
2-1
2
PROGRAMMER
′′
S MODEL
2.1 OVERVIEW
S3C2501X was developed using the advanced ARM9TDMI core designed by advanced RISC machines, Ltd.
— Processor Operating States
From the programmer
′
s point of view, the ARM9TDMI can be in one of two states:
— ARM state which executes 32-bit, word-aligned ARM instructions.
— THUMB state which operates with 16-bit, half-word-aligned THUMB instructions. In this state, the PC uses
bit 1 to select between alternate half-words.
NOTE
Transition between these two states does not affect the processor mode or the contents of the registers.
2.2 SWITCHING STATE
2.2.1 ENTERING THUMB STATE
Entry into THUMB state can be achieved by executing a BX instruction with the state bit (bit 0) set in the operand
register.
Transition to THUMB state will also occur automatically on return from an exception (IRQ, FIQ, UNDEF, ABORT,
SWI etc.), if the exception was entered with the processor in THUMB state.
2.2.2 ENTERING ARM STATE
Entry into ARM state happens:
1.
On execution of the BX instruction with the state bit clear in the operand register.
2.
On the processor taking an exception (IRQ, FIQ, RESET, UNDEF, ABORT, SWI etc.). In this case, the PC is
placed in the exception mode
′
s link register, and execution commences at the exception
′
s vector address.
Summary of Contents for S3C2501X
Page 18: ......
Page 275: ...MEMORY CONTROLLER S3C2501X 5 60 NOTES ...
Page 289: ...I2C CONTROLLER S3C2501X 6 14 NOTES ...
Page 373: ...GDMA CONTROLLER S3C2501X 9 24 NOTES ...
Page 435: ...I O PORTS S3C2501X 12 12 NOTES ...