Samsung YP-P10 User Manual download pdf (Page 69)

100

101

S3C2440A RISC MICROPROCESSOR PROGRAMMER'S MODEL

2-1

2 PROGRAMMER'S MODEL

OVERVIEW

S3C2440A is developed using the advanced ARM920T core, which has been designed by Advanced RISC Machines,

Ltd.

PROCESSOR OPERATING STATES

From the programmer's point of view, the ARM920T can be in one of the two states:

• ARM state which executes 32-bit, word-aligned ARM instructions

• THUMB state is a state which can execute 16-bit, halfword-aligned THUMB instructions. In this state, the PC

uses bit 1 to select between alternate halfwords

NOTE

Transition between these two states does not affect the processor mode or the contents of the registers.

SWITCHING STATE

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

Transition to THUMB state will also occur automatically on return from an exception (IRQ, FIQ, UNDEF, ABORT,

SWI etc.), if the exception is entered with the processor in THUMB state.

Entering ARM State

Entry into ARM state can be done by the following methods:-

• On execution of the BX instruction with the state bit clear in the operand register.

• 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.

MEMORY FORMATS

ARM920T views memory as a linear collection of bytes numbered upwards from zero. Bytes 0 to 3 hold the first

stored word, bytes 4 to 7 the second and so on. ARM920T can treat words in memory as being stored either in Big-

Endian or Little-Endian format.

1 2 ... 64 65 66 67 68 69 70 71 72 73 74 ... 595 596

Comments to this Manuals

No comments

Samsung YP-P10 User Manual Page 69

Comments to this Manuals

Related products and manuals for MP3/MP4 players Samsung YP-P10