SH7263 Datasheet, PDF (174/1862 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperHTM RISC engine Family / SH7260 Series

Section 5 Exception Handling
5.9 Usage Notes
5.9.1 Value of Stack Pointer (SP)
The value of the stack pointer must always be a multiple of four. If it is not, an address error will
occur when the stack is accessed during exception handling.
5.9.2 Value of Vector Base Register (VBR)
The value of the vector base register must always be a multiple of four. If it is not, an address error
will occur when the stack is accessed during exception handling.
5.9.3 Address Errors Caused by Stacking of Address Error Exception Handling
When the stack pointer is not a multiple of four, an address error will occur during stacking of the
exception handling (interrupts, etc.) and address error exception handling will start up as soon as
the first exception handling is ended. Address errors will then 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
shifted to the address error exception service routine and enables error processing.
When an address error occurs during exception handling stacking, the stacking bus cycle (write) is
executed. During stacking of the status register (SR) and program counter (PC), the SP is
decremented by 4 for both, so the value of SP will not be a multiple of four after the stacking
either. The address value output during stacking is the SP value, so the address where the error
occurred is itself output. This means the write data stacked will be undefined.
Rev. 2.00 Mar. 14, 2008 Page 140 of 1824
REJ09B0290-0200