M37735MHB Datasheet, PDF (15/90 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

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MITSUBISHI MICROCOMPUTERS
M37735MHBXXXFP
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
By setting the port function control register, the INT2/Key input interrupt
function can be switched to the key input interrupt function which
uses the KI0 to KI3 inputs. Figure 11 shows the bit configuration of the
port function control register, and Figure 12 shows the INT2/Key input
interrupt input circuit block diagram.
When the key input interrupt selection bit of the port function control
register is “0”, a signal is input from the INT2 pin to the INT2 /Key input
interrupt control circuit and the INT2 interrupt is normally performed.
When the key input interrupt selection bit is “1”, signals input from
the KI0 to KI3 pins are inverted, and then the logical sum of these
signals is input to the INT2 interrupt control circuit. In this case, the
external interrupt which uses the KI0 to KI3 pins is performed. (Pins
KI0 to KI3 correspond to ports P54 to P57, respectively.) Additionally,
by setting the port P6 pull-up selection bit 1 to “1”, the INT2 input is
added to that logical sum, so that the external interrupt which uses
the inputs KI0 to KI3 and INT2 is performed. When using the key input
interrupt, it is necessary to select the edge sense which uses the
falling edge by setting the INT2 /Key input interrupt control register.
Because of this selection, a key input interrupt request occurs when
“L” is input to one of the KI0 to KI3 and INT2 pins. The interrupt vector
and the interrupt control register are common to the INT2 and key
input interrupts.
Pull-up resistors (transistors) can be added to the KI0 to KI3 pins by
setting “1” to the port P5 pull-up selection bit and “0” to the contents
of the port P5i (i = 4 to 7) direction register. Similarly, a pull-up resistor
can be added to the INT2 pin by setting “1” to the port P6 pull-up
selection bit 1 and “0” to the content of the port P64 direction register.
With the key input interrupt and the pull-up function, the key input
circuit is easily composed.
P64/INT2
Pull–up
transistor
P57/KI3
P56/KI2
P55/KI1
P54/KI0
Port P6 pull-up
selection bit 1
Port P64 direction register
Port P6 pull-up
selection bit 1
Port P5 pull-up
selection bit
0
Port P57 direction
register
INT2/Key input interrupt control register (Address 7F16)
When the key input interrupt is
selected, it is necessary to
select the edge sense which
uses falling edge.
Pull–up
transistor
Pull–up
transistor
10
Interrupt control register
1
Key input interrupt selection bit
INT2/Key input
interrupt request
Pull–up
transistor
Fig. 12 INT2 /Key input interrupt input circuit block diagram
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