HCS12 datasheet(356/452 Pages) FREESCALE

356 / 452 page

S12CPUV2 Reference Manual, Rev. 4.0

356

Freescale Semiconductor

Figure 9-9. REV Instruction Flow Diagram

1.0 - O

READ PROGRAM WORD IF $18 MISALIGNED

2.0 - r

READ BYTE @ 0,X (RULE ELEMENT Rx)

X = X + 1 POINT AT NEXT RULE ELEMENT

START

END

4.0 - t

THEN READ BYTE @ Rx,Y (FUZZY IN OR OUT Fy)

5.2 - f

NO BUS ACCESS

ADJUST PC TO POINT AT CURRENT REV INSTRUCTION

IF Rx $FE OR $FF

YES

5.0 - t

READ BYTE @ 0,X (RULE ELEMENT Rx)

Rx = $FF, OTHER?

$FF

OTHER

X = X + 1 POINT AT NEXT RULE ELEMENT

6.2 - f

NO BUS ACCESS

ADJUST X = X – 1

CONTINUE TO INTERRUPT STACKING

V-BIT

0 (MIN)

1 (MAX)

6.0 - x

NO BUS ACCESS

IF Rx $FE THEN A = MIN(A, Fy)

6.1 - x

IF Rx $FE OR $FF, AND ACCA > Fy

THEN WRITE BYTE @ Rx,Y

ELSE NO BUS ACCESS

Rx = $FF (END OF RULES)?

YES

7.0 - O

READ PROGRAM WORD IF $3A MISALIGNED

3.0 - f

NO BUS ACCESS

IF Rx = $FE & V WAS 1, RESET ACCA TO $FF

IF Rx = $FE TOGGLE V-BIT

ELSE NO BUS ACCESS

ELSE A = A (NO CHANGE TO A)

UPDATE RX WITH VALUE READ IN CYC 2 OR 5

INTERRUPT PENDING?

UPDATE FY WITH VALUE READ IN CYC 4.0

UPDATE Fy WITH VALUE READ IN CYC 4.0

HCS12 Datasheet(PDF) 356 Page - Freescale Semiconductor, Inc

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