Motorola MC68340 사용자 설명서
3- 36
MC68340 USER’S MANUAL
MOTOROLA
S0
S2
S4
S0
S2
S4
INTERNAL
PROCESSING
STACK
WRITE
WRITE
WRITE
CYCLE
CLKOUT
DSACKx
R/W
AS
DS
BERR
FC3–FC0
D15–D0
A31–A0
Figure 3-18. Late Bus Error with
DSACK
≈
3.5.2 Retry Operation
When both
BERR
and
HALT
are asserted by an external device during a bus cycle, the
MC68340 enters the retry sequence shown in Figure 3-19. A delayed retry, which is
similar to the delayed
similar to the delayed
BERR
signal described previously, can also occur (see Figure 3-20).
The MC68340 terminates the bus cycle, places the control signals in their inactive state,
and does not begin another bus cycle until the
and does not begin another bus cycle until the
BERR
and
HALT
signals are negated by
external logic. After a synchronization delay, the MC68340 retries the previous cycle using
the same access information (address, function code, size, etc.).
the same access information (address, function code, size, etc.).
BERR
should be negated
before S2 of the retried cycle to ensure correct operation of the retried cycle.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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