HD6417618 datasheet(111/646 Pages) RENESAS

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Section 5 Exception Handling

Rev. 6.00 Jun. 12, 2007 Page 79 of 610

REJ09B0131-0600

5.8

Usage Notes

5.8.1

Value of Stack Pointer (SP)

The SP value must always be a multiple of 4. If it is not, an address error will occur when the

stack is accessed during exception handling.

5.8.2

Value of Vector Base Register (VBR)

The VBR value must always be a multiple of 4. If it is not, an address error will occur when the

stack is accessed during exception handling.

5.8.3

Address Errors Caused by Stacking for Address Error Exception Handling

When the SP value is not a multiple of 4, an address error will occur when stacking for exception

handling (interrupts, etc.) and address error exception handling will start after the first exception

handling is ended. Address errors will also occur in the stacking for this address error exception

handling. To ensure that address error exception handling does not go into an endless loop, no

address errors are accepted at that point. This allows program control to be passed to the handling

routine for address error exception and enables error processing.

When an address error occurs during exception handling stacking, the stacking bus cycle (write) is

executed. When stacking the SR and PC values, the SP values for both are subtracted by 4,

therefore, the SP value is still not a multiple of 4 after the stacking. The address value output

during stacking is the SP value whose lower two bits are cleared to 0. So the write data stacked is

undefined.

5.8.4

Notes on Slot Illegal Instruction Exception Handling

Some specifications on slot illegal instruction exception handling in this LSI differ from those on

the conventional SH2.

• Conventional SH2: Instructions LDC Rm,SR and LDC.L @Rm+,SR are not subject to the slot

illegal instructions.

• This LSI: Instructions LDC Rm,SR and LDC.L @Rm+,SR are subject to the slot illegal

instructions.

The supporting status on our software products regarding this note is as follows:

HD6417618 Datasheet(PDF) 111 Page - Renesas Technology Corp