Working Modes

The EXP bit in the SR is set(if not already), thereby enabling the Exception Stack Pointer (ESP) as the active SP.

The PC and previous SR are pushed on the active (ESP) stack.

The PC jumps to the Vector Base Address (VBA) + Exception Offset Address. For example, executing a TRAP instruction causes the core to enter an Exception state and begin executing instructions at VBA + 0x00, since the TRAP instruction has an exception offset address of 0x00.

If choosing to prepare the return values on the stack explicitly to perform this transition, the programmer should be aware that in Normal mode RTE uses the active stack (NSP).

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SC140 DSP Core Reference Manual

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Freescale Semiconductor SC140 specifications Working Modes