Section 5 Exception Handling
Rev. 3.00 Sep. 27, 2007 Page 76 of 758
REJ09B0243-0300
4. The values fetched from the exception handling vector table are set in PC and SP, then the
program starts.
Be certain to always perform power-on reset exception handling when turning the system power
on.
Power-On Reset by WDT:
When WTCNT of the WDT overflows while a setting is made so that
a power-on reset can be generated in watchdog timer mode of the WDT, this LSI enters the
power-on reset state.
The frequency control register (FRQCR) in the clock pulse generator (CPG) and the watchdog
timer (WDT) registers are not initialized by a reset generated by the WDT (these registers are only
initialized by a power-on reset from the
RES
pin).
If a reset caused by the signal input on the
RES
pin and a reset caused by a WDT overflow occur
simultaneously, the
RES
pin reset has priority, and the WOVF bit in RSTCSR is cleared to 0.
When the power-on reset exception handling caused by the WDT is started, the CPU operates as
follows:
1. The initial value (execution start address) of the program counter (PC) is fetched from the
exception handling vector table.
2. The initial value of the stack pointer (SP) is fetched from the exception handling vector table.
3. The vector base register (VBR) is cleared to H'00000000 and the interrupt mask bits (I3 to I0)
of the status register (SR) are set to H'F (B'1111).
4. The values fetched from the exception handling vector table are set in the PC and SP, then the
program starts.
5.2.3 Manual
Reset
When the
RES
pin is high and the
MRES
pin is driven low, the LSI becomes to be a manual reset
state. To reliably reset the LSI, the
MRES
pin should be kept at low for at least the duration of the
oscillation settling time that is set in WDT when in software standby mode (when the clock is
halted) or at least 20 t
cyc
when the clock is operating. During manual reset, the CPU internal status
is initialized. Registers of on-chip peripheral modules are not initialized. See appendix A, Pin
States, for the status of individual pins during manual reset mode.
In the manual reset status, manual reset exception processing starts when the
MRES
pin is first
kept low for a set period of time and then returned to high. The CPU will then operate in the same
procedures as described for power-on resets.
Summary of Contents for SH7124 R5F7124
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Page 36: ...Section 1 Overview Rev 3 00 Sep 27 2007 Page 16 of 758 REJ09B0243 0300 ...
Page 68: ...Section 2 CPU Rev 3 00 Sep 27 2007 Page 48 of 758 REJ09B0243 0300 ...
Page 108: ...Section 5 Exception Handling Rev 3 00 Sep 27 2007 Page 88 of 758 REJ09B0243 0300 ...
Page 166: ...Section 7 User Break Controller UBC Rev 3 00 Sep 27 2007 Page 146 of 758 REJ09B0243 0300 ...
Page 724: ...Section 20 List of Registers Rev 3 00 Sep 27 2007 Page 704 of 758 REJ09B0243 0300 ...
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