M306V2EEFS datasheet(60/271 Pages) RENESAS

60 / 271 page

Rev.1.40

Oct 06, 2004 page 60 of 269

M306V2ME-XXXFP, M306V2EEFP

The operation of saving registers carried out in the interrupt sequence is dependent on whether the

content of the stack pointer, at the time of acceptance of an interrupt request, is even or odd. If the

content of the stack pointer (Note) is even, the content of the flag register (FLG) and the content of the

program counter (PC) are saved, 16 bits at a time. If odd, their contents are saved in two steps, 8 bits at

a time. Figure 2.7.7 shows the operation of the saving registers.

Note: Stack pointer indicated by U flag.

Figure 2.7.7 Operation of saving registers

(2) Stack pointer (SP) contains odd number

[SP]

(Odd)

[SP] – 1 (Even)

[SP] – 2(Odd)

[SP] – 3 (Even)

[SP] – 4(Odd)

[SP] – 5 (Even)

Address

Sequence in which order

registers are saved

(2)

(1)

Finished saving registers

in four operations.

(3)

(4)

(1) Stack pointer (SP) contains even number

[SP]

(Even)

[SP] – 1(Odd)

[SP] – 2 (Even)

[SP] – 3(Odd)

[SP] – 4 (Even)

[SP] – 5 (Odd)

Note: [SP] denotes the initial value of the stack pointer (SP) when interrupt request is acknowledged.

After registers are saved, the SP content is [SP] minus 4.

Address

Program counter (PCM)

Stack area

Flag register (FLGL)

Program counter (PCL)

Sequence in which order

registers are saved

(2) Saved simultaneously,

all 16 bits

(1) Saved simultaneously,

all 16 bits

Finished saving registers

in two operations.

Program counter (PCM)

Stack area

Flag register (FLGL)

Program counter (PCL)

Saved simultaneously,

all 8 bits

Flag register

(FLGH)

Program

counter (PCH)

Flag register

(FLGH)

Program

counter (PCH)

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