Renesas SH7781 User Manual

Page 123

5. Exception Handling

Rev.1.00 Jan. 10, 2008 Page 93 of 1658

REJ09B0261-0100

5.2.4

Non-Support Detection Exception Register (EXPMASK)

The non-support detection exception register (EXPMASK) is used to enable or disable the
generation of exceptions in response to the use of any of functions 1 to 3 listed below. The
functions of 1 to 3 are planned not to be supported in the future SuperH-family products. The
exception generation functions of EXPMASK can be used in advance of execution; the detection
function then checks for the use of these functions in the software. This will ease the transfer of
software to the future SuperH-family products that do not support the respective functions.

1. Handling of an instruction other than the NOP instruction in the delay slot of the RTE

instruction.

2. Handling of the SLEEP instruction in the delay slot of the branch instruction.

3. Performance of IC/OC memory-mapped associative write operations.

According to the value of EXPMASK, functions 1 and 2 can generate a slot illegal instruction
exception, and 3 can generate a data address error exception.

Generation of each exception can be disabled by writing 1 to the corresponding bit in EXPMASK.
However, it is recommended that the above functions should not be used when making a program
to maintain the compatibility with the future products.

Use the store instruction of the CPU to update EXPMASK. After updating the register and then
reading the register once, execute either of the following instructions. Executing either instruction
guarantees the operation with the updated register value.

• Execute the RTE instruction.
• Execute the ICBI instruction for any address (including non-cacheable area).

Bit:

Initial value:

R/W:

Bit:

Initial value:

R/W:

R/W

−

CAW

−

BRDS

SLP

RTE

−