MC68020 Motorola, MC68020 Datasheet - Page 101

• Manufacturer Part Number: MC68020
• Description: (MC68020 / MC68EC020) MICROPROCESSORS USERS MANUAL
• Manufacturer: Motorola

The acceptable bus cycle terminations for asynchronous cycles are summarized in
relation to DSACK1/DSACK0 assertion as follows (case numbers refer to Table 5-8):
Normal Termination:
Halt Termination:
Bus Error Termination:
Retry Termination:
Legend:
5-54
Case No.
DSACK1/DSACK0 is asserted; BERR and HALT remain negated (case 1).
HALT is asserted at same time or before DSACK1/DSACK0, and BERR remains
negated (case 2).
BERR is asserted in lieu of, at the same time, or before DSACK1/DSACK0 (case 3) or
after DSACK1/DSACK0 (case 4), and HALT remains negated; BERR is negated at the
same time or after DSACK1/DSACK0.
HALT and BERR are asserted in lieu of, at the same time, or before DSACK1/DSACK0
(case 5) or after DSACK1/DSACK0 (case 6); BERR is negated at the same time or after
DSACK1/DSACK0; HALT may be negated at the same time or after BERR.
n—The number of current even bus state (e.g., S2, S4, etc.)
A—Signal is asserted in this bus state
N—Signal is not asserted and/or remains negated in this bus state
X—Don’t care
S—Signal was asserted in previous state and remains asserted in this state
1
2
3
4
5
6
DSACK1/DSACK0
DSACK1/DSACK0
DSACK1/DSACK0
DSACK1/DSACK0
DSACK1/DSACK0
DSACK1/DSACK0
Table 5-8.
Control Signal
BERR
BERR
BERR
BERR
BERR
BERR
HALT
HALT
HALT
HALT
HALT
HALT
DSACK1/DSACK0
Asserted on Rising
A/S
N/A
N/A
A/S
A
N
N
A
N
A
N
A
N
N
A
A
N
N
n
Edge of State
M68020 USER’S MANUAL
n+2
,
S
N
X
S
N
S
X
S
N
X
A
N
X
S
S
X
A
A
BERR
Normal cycle terminate and continue.
Normal cycle terminate and halt. Continue when
HALT negated.
Terminate and take bus error exception, possibly
deferred.
Terminate and take bus error exception, possibly
deferred.
Terminate and retry when HALT negated.
Terminate and retry when HALT negated.
,
HALT
Assertion Results
Result
MOTOROLA