MITSUBISHI MICROCOMPUTERS
Ne
pro
w
d
uct
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
5E
16
) 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
5F
16
).
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.
Internal clock
A
i
/D
i
Address
Data
Address
Data
Wait bit “1”
(No wait)
RDE
or
WEL
,
WEH
ALE
Access time
A
i
/D
i
Address
Data
Address
Data
Wait bit “0”
(Wait 1)
RDE
or
WEL
,
WEH
ALE
Access time
A
i
/D
i
Address
Data
Address
Microprocessor
mode
00
16
SFR
80
16
RAM
87F
16
Wait bit “0”
(Wait 0)
RDE
or
WEL
,
WEH
ALE
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”.
FFFFFF
16
The shaded area is the external memory area.
Note that banks 10
16
to FF
16
cannot be accessed.
Fig. 10 External memory area for microprocessor mode
12
RENESAS [ RENESAS TECHNOLOGY CORP ]
