S3C4530A datasheet(30/432 Pages) SAMSUNG | 16/32-bit RISC microcontroller is a cost-effective, high-performance microcontroller

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PROGRAMMER'S MODEL

S3C4530A

2-4

REGISTERS

ARM7TDMI has a total of 37 registers-31 general-purpose 32-bit registers and six status registers - but these

cannot all be seen at once. The processor state and operating mode dictate which registers are available to the

programmer.

The ARM State Register Set

In ARM state, 16 general registers and one or two status registers are visible at any one time. In privileged (non-

User) modes, mode-specific banked registers are switched in. Figure 2-3 shows which registers are available in

each mode: the banked registers are marked with a shaded triangle.

The ARM state register set contains 16 directly accessible registers: R0 to R15. All of these except R15 are

general-purpose, and may be used to hold either data or address values. In addition to these, there is a

seventeenth register used to store status information.

is used as the subroutine link register. This receives a copy of R15 when a branch

and link (BL) instruction is executed. At all other times it may be treated as a

general-purpose register. The corresponding banked registers R14_svc, R14_irq,

R14_fiq, R14_abt and

R14_und are similarly used to hold the return values of

R15 when interrupts and exceptions arise, or when branch and link instructions are

executed within interrupt or exception routines.

holds the Program Counter (PC). In ARM state, bits [1:0] of R15 are zero and bits

[31:2] contain the PC. In THUMB state, bit [0] is zero and bits [31:1] contain the PC.

is the CPSR (Current Program Status Register). This contains condition code flags

and the current mode bits.

FIQ mode has seven banked registers mapped to R8-14 (R8_fiq-R14_fiq). In ARM state, many FIQ handlers do

not need to save any registers. User, IRQ, Supervisor, Abort and Undefined each have two banked registers

mapped to R13 and R14, allowing each of these modes to have a private stack pointer and link registers.

S3C4530A Datasheet(PDF) 30 Page - Samsung semiconductor