SH7211 Datasheet, PDF (110/1228 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer SuperHTM RISC engine Family

Section 5 Exception Handling
5.2.3 Manual Reset
(1) Manual Reset by Means of MRES Pin
When the MRES pin is driven low, this LSI enters the manual reset state. To reset this LSI without
fail, the MRES pin should be kept at the low level for at least 20-tcyc. In the manual reset state,
the CPU’s internal state is initialized, but all the on-chip peripheral module registers are not
initialized. In the manual reset state, manual reset exception handling starts when the MRES pin is
first driven low for a fixed period and then returned to high. 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, the interrupt mask level bits (I3 to
I0) of the status register (SR) are initialized to H'F (B'1111), and the BO and CS bits are
initialized. The BN bit in IBNR of the INTC is also initialized to 0.
4. The values fetched from the exception handling vector table are set in the PC and SP, and the
program begins executing.
(2) Manual Reset Initiated by WDT
When a setting is made for a manual reset to be generated in the WDT’s watchdog timer mode,
and WTCNT of the WDT overflows, this LSI enters the manual reset state.
When manual reset exception processing is started by the WDT, the CPU operates in the same
way as when a manual reset was caused by the MRES pin.
When a manual reset is generated, the bus cycle is retained, but if a manual reset occurs while the
bus is released or during DMAC burst transfer, manual reset exception handling will be deferred
until the CPU acquires the bus. However, if the interval from generation of the manual reset until
the end of the bus cycle is equal to or longer than the fixed internal manual reset interval cycles,
the internal manual reset source is ignored instead of being deferred, and manual reset exception
handling is not executed.
Rev. 2.00 May. 08, 2008 Page 86 of 1200
REJ09B0344-0200