MC68LC040RC25A Datasheet, PDF (60/442 Pages) Freescale Semiconductor, Inc – M68040 Users Manual

Freescale Semiconductor, Inc.
FETCH DESCRIPTOR &
UPDATE HISTORY AND STATUS
TYPE = 'PAGE' OR 'POINTER'
FETCH DESCRIPTOR
AT PA = TA + (INDEX*4)
(INDEX = RI, PI, OR PGI)
IF SCHEDULED, EXECUTE
WRITE ACCESS (U 1) FOR
PREVIOUS DESCRIPTOR
(SEE NOTE)
TYPE = 'INDIRECT'
FETCH DESCRIPTOR AT
PA = DESCRIPTOR ADDRESS
OTHERWISE
CREATE ATC ENTRY
WITH R-BIT CLEAR
NORMAL TERMINATION
OF ALL BUS TRANSFERS
EXIT TABLE SEARCH
TYPE =
'POINTER'
TYPE = 'PAGE'
OR 'INDIRECT'
'INVALID'
'RESIDENT'
RETURN
WP = WP V W
'INVALID'
OR 'INDIRECT'
'RESIDENT'
WP = WP V W
RETURN
U=0
SCHEDULE
WRITE ACCESS
U1
(SEE NOTE)
U=1
RETURN
READ ACCESS
WRITE ACCESS
U=0
U=0&
(WP = 1 OR M = 1)
U=1&
(WP = 1 OR M = 1)
U=1
WP = 0 & M = 0
EXECUTE
LOCKED
RMW ACCESS
U1
EXECUTE
WRITE ACCESS
U 1, M 1
NOTE : ^{DUE TO ACCESS PIPELINING, A POINTER}
DESCRIPTOR WRITE ACCESS TO UPDATE
THE U-BIT OCCURS AFTER THE READ OF
THE NEXT LEVEL DESCRIPTOR.
ABBREVIATIONS:
WP – ACCUMULATED WRITE-
PROTECTION STATUS
V – LOGICAL "OR" OPERATOR
– ASSIGNMENT OPERATOR
OTHERWISE
NORMAL TERMINATION
OF ALL BUS TRANSFERS
CREATE ATC ENTRY
WITH R-BIT CLEAR
RETURN
EXIT TABLE SEARCH
Figure 3-10. Detailed Flowchart of Descriptor Fetch Operation
MOTOROLA
M68040 USER'S MANUAL
For More Information On This Product,
Go to: www.freescale.com
3-11