Operation Description - Renesas 7700 FAMILY User Manual

CONNECTION WITH EXTERNAL DEVICES

12.4.1 Operation description

Judgment timing of the input level of the HOLD pin depends on the state using the bus. While the bus is
not in use, the judgment is performed at every falling of φ
depends on the bus cycle. Table 12.4.2 lists the judgment timing of the input level of the HOLD pin during
the used bus.
Additionally, when accessing word data beginning from an odd address with 2-bus cycle, the judgment is
performed only at the second bus cycle. (See Figure 12.4.1.)
When "L" level is detected at judgment of the input level, the microcomputer enters Hold state. (This is
called acceptance of Hold request.)
When the Hold request is accepted, φ
changes "H" to "L". When 1 cycle of φ
___
BHE, and the external bus become floating state.
In Hold state, the input level of the HOLD pin is judged at every falling of φ
_____
detected, the HLDA pin's level changes "L" to "H" next rising of φ
_____
the level of HLDA pin becomes "H", the microcomputer terminates Hold state.
Figures 12.4.2 to 12.4.4 show timing of acceptance of Hold request and termination of Hold state.
Note: φ has a same polarity and a same frequency as the clock φ
BIU
of the Ready request, or executing the STP or WIT instruction. Accordingly, judgment of the input
_____
level of the HOLD pin is not performed during Ready state.
Judgment timing of input level to HOLD pin
Fig. 12.4.1 Judgment when accessing word data beginning from odd address with 2-bus cycle
_____
BIU
stops next rising of φ
CPU
has passed after the level of HLDA pin becomes "L", pins R/W,
BIU
_____
No judge
Clock
1
BIU
E
ALE
Reading A
Writing
A W
Accessing word data with 2-bus cycle.
(Example of 2
7751 Group User's Manual
. While the bus is in use, the judgment timing
. At the same time, the HLDA pin's level
BIU
_____
. Then, when "H" level is
BIU
. When 1 cycle of φ
BIU
. However, φ
1
Judge
A
A W
access in low-speed running
12.4 Hold function
_____
_____
__
has passed after
BIU
stops by acceptance
BIU
)
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