OVERVIEW
7733 Group User’s Manual
1-9
1.3 Pin description
(2) In memory expansion mode
Table 1.3.5 Examples of handling unused pins in memory expansion mode
Pins
P42–P47, P5–P8
____
BHE
(Note 3)
ALE
(Note 4)
_____
HLDA
XOUT (Note 6)
_____
____
HOLD
, RDY
AVcc
AVss, VREF
Handling example
Connect these pins to pin Vcc or Vss via resistors after these
pins are set to the input mode, or leave these pins open after
they are set to the output mode (Notes 1, 2, and 7).
Leave this pin open. (Note 5)
Leave this pin open.
Connect these pins to pin Vcc via resistors after these pins are
set to the input mode. (These pins are pulled high.) (Note 2)
Connect this pin to pin Vcc.
Connect these pins to pin Vss.
Notes 1: When leaving these pins open after they are set to the output mode, note the following: these pins
function as input ports from reset until they are switched to the output mode by software. Therefore,
voltage levels of these pins are undefined and the power source current may increase while these
pins function as input ports. Software reliability can be enhanced when the contents of the above
ports’ direction registers are set periodically. This is because these contents may be changed by
noise, a program runaway which occurs owing to noise, etc.
2: For unused pins, use the shortest possible wiring (within 20 mm from the microcomputer’s pins).
3: This is applied when “H” level is input to pin BYTE.
4: This is applied when “H” level is input to pin BYTE and the accessible area has a capacity of 64
Kbytes.
5: When Vss level is applied to pin CNVss, note the following: this pin functions as an input port from
reset until the processor mode is switched to the memory expansion mode by software. Therefore,
a voltage level of this pin is undefined and the power source current may increase while this pin
functions as an input port.
6: This is applied when an external clock is input to pin XIN.
7: Set pin P42/
φ1 as pin P42. (Clock φ1 output is disabled.) And then, for this pin, do the same
handling as that for pins P43 to P47 and P5 to P8.
P42–P47, P5–P8
AVss
VREF
HOLD
RDY
Left open
M37733MHBXXXFP
HLDA
Vcc
Vss
AVcc
XOUT
When setting ports to input mode
Left open
P42–P47, P5–P8
AVs
s
VREF
Left open
Vss
AVcc
XOUT
When setting ports to output mode
Left open
Vcc
M37733MHBXXXFP
BHE
ALE
HOLD
RDY
BHE
ALE
HLDA
Fig. 1.3.2 Examples of handling unused pins in memory expansion mode