Hardware Exception-Handling Sequence; Exception Factors And Vector Table - Hitachi H8/500 Series Hardware Manual

4.1.2 Hardware Exception-Handling Sequence

The hardware exception-handling sequence varies depending on the type of exception. When
exception handling is initiated by a factor other than a reset, the CPU:
1. Saves the program counter and status register (in minimum mode) or program counter, code
page register, and status register (in maximum mode) to the stack.
2. Clears the T bit in the status register to "0."
3. Fetches the start address of the exception-handling routine from the exception vector table.
4. Branches to that address.
For an interrupt, the CPU also alters the interrupt mask level in bits I2 to I0 of the status register.
For a reset, step 1 is omitted. See section 4.2, "Reset," for the full reset sequence.

4.1.3 Exception Factors and Vector Table

The factors that initiate exception handling can be classified as shown in figure 4-1.
The starting addresses of the exception-handling routines for each factor are contained in an
exception vector table located in the low addresses of page 0. The vector addresses are listed in
table 4-2. Note that there are different addresses for the minimum and maximum modes.
82
Downloaded from Elcodis.com electronic components distributor