mc68hc916y3 Freescale Semiconductor, Inc, mc68hc916y3 Datasheet - Page 144

• Manufacturer Part Number: mc68hc916y3
• Description: Mc68hc16y3 16 Bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

5.6.5.1 Bus Errors
5-36
MOTOROLA
BUS ERROR 1
BUS ERROR 2
BUS ERROR 3
BUS ERROR 4
The CPU16 treats bus errors as a type of exception. Bus error exception processing
begins when the CPU16 detects assertion of the IMB BERR signal.
BERR assertions do not force immediate exception processing. The signal is synchro-
nized with normal bus cycles and is latched into the CPU16 at the end of the bus cycle
in which it was asserted. Because bus cycles can overlap instruction boundaries, bus
error exception processing may not occur at the end of the instruction in which the bus
cycle begins. Timing of BERR detection/acknowledge is dependent upon several
factors:
Because of these factors, it is impossible to predict precisely how long after occur-
rence of a bus error the bus error exception is processed.
NOTES:
Termination
NORMAL
1. S = The number of current even bus state (for example, S2, S4, etc.)
2. A = Signal is asserted in this bus state.
3. NA = Signal is not asserted in this state.
4. RA = Signal was asserted in previous state and remains asserted in this state.
5. X = Don’t care
Type of
HALT
• Which bus cycle of an instruction is terminated by assertion of BERR.
• The number of bus cycles in the instruction during which BERR is asserted.
• The number of bus cycles in the instruction following the instruction in which
• Whether BERR is asserted during a program space access or a data space
BERR is asserted.
access.
Table 5-13 DSACK, BERR, and HALT Assertion Results
Control
DSACK
DSACK
DSACK
DSACK
DSACK
DSACK
Signal
BERR
BERR
BERR
BERR
BERR
BERR
HALT
HALT
HALT
HALT
HALT
HALT
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A/RA
NA/A
NA/A
Asserted on Rising
NA
A/S
NA
NA
NA
NA
NA
NA
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S
A
A
A
A
A
A
A
1
2
Edge of State
3
S + 2
RA
NA
RA
NA
RA
RA
RA
NA
RA
RA
X
X
X
X
X
X
A
A
5
4
Normal cycle terminate and continue.
Normal cycle terminate and halt.
Continue when HALT is negated.
Terminate and take bus error exception.
Terminate and take bus error exception.
Terminate and take bus error exception.
Terminate and take bus error exception.
Description
of Result
MC68HC16Y3/916Y3
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