Motorola M68000 User Manual download pdf (Page 226)

Supervisor (Privileged) Instructions

MOTOROLA M68000 FAMILY PROGRAMMER’S REFERENCE MANUAL 6-63

PTEST Test a Logical Address PTEST

(MC68030 only)

Operation: If Supervisor State

Then Logical Address Status → MMUSR

Else TRAP

Assembler PTESTR FC, < ea > ,# < level >

Syntax: PTESTR FC, < ea > ,# < level > ,An

PTESTW FC, < ea > ,# < level >

PTESTW FC, < ea > ,# < level > ,An

Attributes: Unsized

Description: This instruction searches the address translation cache or the translation

tables to a speciﬁed level. Searching for the translation descriptor corresponding to the

< ea > ﬁeld, it sets the bits of the MMU status register according to the status of the

descriptor. Optionally, PTEST stores the physical address of the last table entry

accessed during the search in the speciﬁed address register. The PTEST instruction

searches the address translation cache or the translation tables to obtain status

information, but alters neither the used or modiﬁed bits of the translation tables nor the

address translation cache. When the level operand is zero, only the transparent

translation of either read or write accesses causes the operations of the PTESTR and

PTESTW to return different results.

The < function code > operand is speciﬁed as one of the following:

1. Immediate—Three bits in the command word.

2. Data Register—The three least signiﬁcant bits of the data register speciﬁed in

the instruction.

3. Source Function Code (SFC) Register

4. Destination Function Code (DFC) Register

The effective address is the address to test. The < level > operand specifies the level

of the search. Level 0 specifies searching the addrass translation cache only. Levels

1–7 specify searching the translation tables only. The search ends at the specified

level. A level 0 test does not return the same MMU status register values as a test at a

nonzero level number.

Execution of the instruction continues to the requested level or until detecting one of

the following conditions:

• Invalid Descriptor

• Limit Violation

• Bus Error Assertion (Physical Bus Error)

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Motorola M68000 User Manual Page 226