D950-CORE datasheet(28/89 Pages) STMICROELECTRONICS

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D950-Core

SWI

Non maskable (internally vectorized) software interrupt SWI is a 3-cycle instruction whose

interrupt routine address is 0x0002. Return from the SWI routine is performed through RTI.

The SWI routine is non-interruptible by an external interrupt request.

Note:

IT should not be asserted low if a previous request has not been acknowledged. In this case,

the previous request will not be processed.

EI and IPE bits are not affected when STA register is restored.

4.3.5 Loop Controller

Table 4.3

Loop Instruction

Hardware loop resources

The program sequencer includes a powerful hardware loop mechanism. This allows the

nesting of up to three levels of loops by using nine 16-bit registers, organized in three banks

of three registers.

Each bank includes one loop start address register (LS), one loop end address register (LE)

and one loop count register (LC). These registers can be read and written by register move

instructions, allowing extension of the number of nested loops by software.

The currently selected loop register bank is pointed to by bits LSP1 and LSP0 of the CCR.

When the current level changes, this 2-bit register is incremented or decremented through

dedicated instructions (see Section 5.4.5“Conditional Assignment Instruction”) to modify

the bank.

Loop operation: REPEAT instruction

The REPEAT instruction performs automatic management of the different loop registers (LS,

LC, LE and LSP) and defines the number of iterations and address of the last instruction of the

loop.

The loop begins at the instruction following REPEAT. Conditional instructions CONTINUE and

BREAK can be put within a loop. Their effect is to restart (resp. exit from) the loop when the

condition is verified.

Notes

The maximum repeat count value of 216-1 is obtained by setting LC to 0xFFFF.

An endless loop can be set up by initializing LC to: 0x0000 for REPEAT block,

0x0001 for REPEAT single.

Loop Instruction

Body of loop

Loop value

Single instruction

Immediate

REPEAT

Block of instructions

Immediate

Block of instructions

Computed

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