9/29/95
SECTION 1: OVERVIEW
UM Rev.1.0
viii
M68020 USER’S MANUAL
MOTOROLA
TABLE OF CONTENTS (Continued)
Paragraph
Page
Number
Title
Number
3.12
Power Supply Connections .....................................................................3-7
3.13
Signal Summary......................................................................................3-8
Section 4
On-Chip Cache Memory
4.1
On-Chip Cache Organization and Operation ..........................................4-1
4.2
Cache Reset ........................................................................................... 4-3
4.3
Cache Control .........................................................................................4-3
4.3.1
Cache Control Register (CACR) .........................................................4-3
4.3.2
Cache Address Register (CAAR) ........................................................4-4
Section 5
Bus Operation
5.1
Bus Transfer Signals............................................................................... 5-1
5.1.1
Bus Control Signals .............................................................................5-2
5.1.2
Address Bus ........................................................................................ 5-3
5.1.3
Address Strobe ....................................................................................5-3
5.1.4
Data Bus.............................................................................................. 5-3
5.1.5
Data Strobe ......................................................................................... 5-4
5.1.6
Data Buffer Enable ..............................................................................5-4
5.1.7
Bus Cycle Termination Signals............................................................5-4
5.2
Data Transfer Mechanism....................................................................... 5-5
5.2.1
Dynamic Bus Sizing ............................................................................5-5
5.2.2
Misaligned Operands...........................................................................5-14
5.2.3
Effects of Dynamic Bus Sizing and Operand Misalignment ................ 5-20
5.2.4
Address, Size, and Data Bus Relationships ........................................5-21
5.2.5
Cache Interactions ..............................................................................5-22
5.2.6
Bus Operation ..................................................................................... 5-24
5.2.7
Synchronous Operation with DSACK1/DSACK0 ............................... 5-24
5.3
Data Transfer Cycles ..............................................................................5-25
5.3.1
Read Cycle ..........................................................................................5-26
5.3.2
Write Cycle ..........................................................................................5-33
5.3.3
Read-Modify-Write Cycle.....................................................................5-39
5.4
CPU Space Cycles .................................................................................5-44
5.4.1
Interrupt Acknowledge Bus Cycles ......................................................5-45
5.4.1.1
Interrupt Acknowledge Cycle—Terminated Normally ...................... 5-45
5.4.1.2
Autovector Interrupt Acknowledge Cycle .........................................5-48
5.4.1.3
Spurious Interrupt Cycle .................................................................. 5-48
5.4.2
Breakpoint Acknowledge Cycle ...........................................................5-50
5.4.3
Coprocessor Communication Cycles .................................................. 5-53
5.5
Bus Exception Control Cycles................................................................. 5-53
5.5.1
Bus Errors ........................................................................................... 5-55
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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