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CONNECTION WITH EXTERNAL DEVICES
12.3 Ready function
12.3 Ready function
Ready function provides the function to facilitate access to external devices that require a long access time.
By supplying "L" level to the RDY pin in the memory expansion or microprocessor mode, the microcomputer
enters Ready state and retains this state while the RDY pin is at "L" level. Table 12.3.1 lists the microcomputer's
state in Ready state.
In Ready state, the oscillator's oscillation does not stop, so that the internal peripheral devices can operate.
Ready function is valid for the internal and external areas.
Table 12.3.1 Microcomputer's state in Ready state
Item
Oscillation, φ
_
φ
, φ
, E
CPU
BIU
Pins A
to A
, A
/D
to
0
7
8
8
A
/D
, A
/D
to A
/D
15
15
16
0
23
____
_____
BHE, HLDA, ALE
Pins P4
to P4
,
3
7
P5 to P8 (Note)
/ φ
P4
2
1
Watchdog timer
Clock φ
output select bit : Bit 7 at address 5E
1
Note: When this functions as a programmable I/O port.
12–14
____
Operating
Stopped at "L"
Retains the state when Ready request was accepted.
__
, R/W,
7
In the memory expansion mode:
•When clock φ
•When clock φ
Ready request was accepted.
In the microprocessor mode:
•This pin outputs clock φ
Operating
7751 Group User's Manual
____
State
output select bit = "1," this pin outputs clock φ
1
output select bit = "0," this pin retains the state when
1
.
1
16
.
1
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