Datasheet

Section 4 Exception Handling
Rev. 6.00 Mar. 18, 2010 Page 123 of 982
REJ09B0054-0600
4.3.3 Interrupts after Reset
If an interrupt is accepted after a reset and before the stack pointer (SP) is initialized, the PC and
CCR will not be saved correctly, leading to a program crash. To prevent this, all interrupt requests,
including NMI, are disabled immediately after a reset. Since the first instruction of a program is
always executed immediately after the reset state ends, make sure that this instruction initializes
the stack pointer (example: MOV.L #xx,SP).
4.3.4 State of On-Chip Peripheral Modules after Reset Release
After reset release, MSTPCRA is initialized to H'3F, MSTPCRB and MSTPCRC are initialized to
H'FF, and all modules except the DMAC* and DTC enter module stop mode. Consequently, on-
chip peripheral module registers cannot be read or written to. Register reading and writing is
enabled when the module stop mode is exited.
Note: * Supported only by the H8S/2239 Group.
4.4 Traces
Traces are enabled in interrupt control mode 2. Trace mode is not activated in interrupt control
mode 0, irrespective of the state of the T bit. For details of interrupt control modes, see section 5,
Interrupt Controller.
If the T bit in EXR is set to 1, trace mode is activated. In trace mode, a trace exception occurs on
completion of each instruction. Trace mode is not affected by interrupt masking. Table 4.4 shows
the state of CCR and EXR after execution of trace exception handling. Trace mode is canceled by
clearing the T bit in EXR to 0. Interrupts are accepted even within the trace exception handling
routine.
The T bit saved on the stack retains its value of 1, and when control is returned from the trace
exception handling routine by the RTE instruction, trace mode resumes. Trace exception handling
is not carried out after execution of the RTE instruction.