Sq Protection; Reading The Sqs (Sh7750R Only) - Hitachi SH7750 Hardware Manual

Sh7750 series superh risc engine

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SQ Protection

Determination of an exception in a write to an SQ or transfer to external memory (PREF

instruction) is performed as follows according to whether the MMU is on or off. In the SH7750 or

SH7750S, if an exception occurs in an SQ write, the SQ contents may be corrupted. In the

SH7750R, original SQ contents are guaranteed. If an exception occurs in transfer from an SQ to

external memory, the transfer to external memory will be aborted.

• When MMU is on

Operation is in accordance with the address translation information recorded in the UTLB, and

MMUCR.SQMD. Write type exception judgment is performed for writes to the SQs, and read

type for transfer from the SQs to external memory (PREF instruction), and a TLB miss

exception, protection violation exception, or initial page write exception is generated.

However, if SQ access is enabled, in privileged mode only, by MMUCR.SQMD, an address

error will be flagged in user mode even if address translation is successful.

• When MMU is off

Operation is in accordance with MMUCR.SQMD.

0: Privileged/user access possible

1: Privileged access possible

If the SQ area is accessed in user mode when MMUCR.SQMD is set to 1, an address error will

In the SH7750R, a load instruction may be executed in the privileged mode to read the contents of

the SQs from the address range of H'FF001000 to H'FF00103C in the P4 area. Only longword

access is possible.

: H'FF001000

: LW specification : Specification of longword position in SQ0 or SQ1

Rev. 6.0, 07/02, page 124 of 986

: Store queue specification

: 0: SQ0 specification, 1: SQ1 specification

: Fixed at 0

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