M37735S4LHP Datasheet, PDF (13/37 Pages) Mitsubishi Electric Semiconductor – 16-BIT CMOS MICROCOMPUTER

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MITSUBISHI MICROCOMPUTERS
M37735S4LHP
16-BIT CMOS MICROCOMPUTER
• Wait bit
As shown in Figure 11, when the external memory area is accessed
with the wait bit (bit 2 of the processor mode register 0 at address
5E16) cleared to “0”, the access time can be extended compared with
no wait (the wait bit is “1”).
The access time is extended in two ways and this is selected with the
wait selection bit (bit 0 of the processor mode register 1 at address
5F16).
When this bit is “1”, the access time is 1.5 times compared to that for
no wait. When this bit is “0”, the access time is twice compared to
that for no wait.
At reset, the wait bit and the wait selection bit are “0”.
Access to internal memory area is always performed in the no wait
mode regardless of the wait bit.
The processor modes are described below.
Microprocessor
mode
0016
SFR
8016
RAM
87F16
Internal clock
Ai/Di
Wait bit “1” _{RDE or}
(No wait) _{WEL, WEH}
ALE
Address Data Address Data
Ai/Di
Wait bit “0” _{RDE or}
(Wait 1)
WEL, WEH
ALE
Access time
Address Data Address Data
Ai/Di
Wait bit “0” _{RDE or}
(Wait 0)
WEL, WEH
ALE
Access time
Address
Data
Address
Access time
Fig. 11 Relationship between wait bit, wait selection bit, and access time
(1) Microprocessor mode [10]
The microcomputer enters the microprocessor mode after connecting
the CNVss pin to Vcc and starting from reset.
___
___
Pin RDE is the output pin for the read enable signal (RDE).
___
RDE is “L” during the data read term in the read cycle. When the
___
internal memory area is read, RDE can be fixed to “H” by setting the
signal output disable selection bit (bit 6 of the oscillation circuit control
register 0) to “1”.
FFFFFF16
The shaded area is the external memory area.
Note that banks 1016 to FF16 cannot be accessed.
Fig. 10 External memory area for microprocessor mode
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