SH7721 datasheet(284/1524 Pages) RENESAS

284 / 1524 page

Section 7 Exception Handling

Rev. 3.00 Jan. 18, 2008 Page 222 of 1458

REJ09B0033-0300

1. The contents of the SSR are restored into the SR to return to the processing state in effect

before the exception handling took place.

2. A delay slot instruction of the RTE instruction is executed.*

3. Control is passed to the address stored in the SPC.

The above operations from 1 to 3 are executed in sequence. During these operations, no other

exceptions may be accepted. By changing the SPC and SSR before executing the RTE instruction,

a status different from that in effect before the exception handling can also be specified.

Notes: 1. The MMU registers are also modified if an MMU exception occurs.

2. For details on the CPU processing mode in which RTE delay slot instructions are

executed, please refer to section 7.5, Usage Notes.

7.2.2

Exception Vector Addresses

A vector address for general exceptions is determined by adding a vector offset to a vector base

address. The vector offset for general exceptions other than the TLB miss exception is

H'00000100. The vector offset for interrupts is H'00000600. The vector base address is loaded into

the vector base register (VBR) using the software. The vector base address should reside in the P1

or P2 fixed physical address space.

7.2.3

Exception Codes

The exception codes are written to bits 11 to 0 of the EXPEVT (for reset or general exceptions) or

the INTEVT and INTEVT2 (for interrupt requests) to identify each specific exception event. See

section 8, Interrupt Controller (INTC), for details of the exception codes for interrupt requests.

Table 7.1 lists exception codes for resets and general exceptions.

7.2.4

Exception Request and BL Bit (Multiple Exception Prevention)

The BL bit in SR is set to 1 when a reset or exception is accepted. While the BL bit is set to 1,

acceptance of general exceptions is restricted as described below, making it possible to effectively

prevent multiple exceptions from being accepted.

If the BL bit is set to 1, an interrupt request is not accepted and is retained. The interrupt request is

accepted when the BL bit is cleared to 0. If the CPU is in low power consumption mode, an

interrupt is accepted even if the BL bit is set to 1 and the CPU returns from the low power

consumption mode.

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